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1

Clues for biomimetics from natural composite materials  

PubMed Central

Bio-inspired material systems are derived from different living organisms such as plants, arthropods, mammals and marine organisms. These biomaterial systems from nature are always present in the form of composites, with molecular-scale interactions optimized to direct functional features. With interest in replacing synthetic materials with natural materials due to biocompatibility, sustainability and green chemistry issues, it is important to understand the molecular structure and chemistry of the raw component materials to also learn from their natural engineering, interfaces and interactions leading to durable and highly functional material architectures. This review will focus on applications of biomaterials in single material forms, as well as biomimetic composites inspired by natural organizational features. Examples of different natural composite systems will be described, followed by implementation of the principles underlying their composite organization into artificial bio-inspired systems for materials with new functional features for future medicine. PMID:22994958

Lapidot, Shaul; Meirovitch, Sigal; Sharon, Sigal; Heyman, Arnon; Kaplan, David L; Shoseyov, Oded

2013-01-01

2

New toughening concepts for ceramic composites from rigid natural materials.  

PubMed

The mechanisms underlying the toughening in rigid natural composites exhibited by the concentric cylindrical composites of spicules of hexactinellid sponges, and by the nacre (brick-and-mortar) structure of mollusks such as Haliotis rufescens (red abalone), as well as the crossed-lamellar structure of Strombus gigas (queen conch) show commonalities in the manner in which toughening takes place. It is proposed that crack diversion, a new kind of crack bridging, resulting in retardation of delamination, creation of new surface areas, and other energy-dissipating mechanisms occur in both natural systems. However, these are generally different from the toughening mechanisms that are utilized for other classes of structural materials. Complementary to those mechanisms found in rigid natural ceramic/organic composites, special architectures and thin viscoelastic organic layers have been found to play controlling roles in energy dissipation in these structures. PMID:21565715

Mayer, George

2011-07-01

3

Natural frequency and damping behavior of composite materials  

E-print Network

to gain a data base for static and dynamic response of composite components. This project focuses on the vibration and damping characterization of composites in the presence of damage. The effects of selection of material system, size, stacking... and progressive damage accumulation, may make composites an unattractive choice as an alternative to metals, whereas other characteristics such as vibration behavior provide opportunities to tailor structures effectively. Wave propagation and vibration...

Duggan, Matthew Brace

2012-06-07

4

Composite material  

DOEpatents

A composite biocompatible hydrogel material includes a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa. A calcium comprising salt is disposed in at least some of the pores. The porous polymer matrix can comprise cellulose, including bacterial cellulose. The composite can be used as a bone graft material. A method of tissue repair within the body of animals includes the steps of providing a composite biocompatible hydrogel material including a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa, and inserting the hydrogel material into cartilage or bone tissue of an animal, wherein the hydrogel material supports cell colonization in vitro for autologous cell seeding.

Hutchens, Stacy A. (Knoxville, TN); Woodward, Jonathan (Solihull, GB); Evans, Barbara R. (Oak Ridge, TN); O'Neill, Hugh M. (Knoxville, TN)

2012-02-07

5

Investigation of Polymer Resin/Fiber Compatibility in Natural Fiber Reinforced Composite Automotive Materials  

SciTech Connect

Natural fibers represent a lower density and potentially lower cost alternative to glass fibers for reinforcement of polymers in automotive composites. The high specific modulus and strength of bast fibers make them an attractive option to replace glass not only in non-structural automotive components, but also in semi-structural and structural components. Significant barriers to insertion of bast fibers in the fiber reinforced automotive composite market include the high moisture uptake of this lignocellulosic material relative to glass and the weak inherent interface between natural fibers and automotive resins. This work seeks to improve the moisture uptake and resin interfacing properties of natural fibers through improved fundamental understanding of fiber physiochemical architecture and development of tailored fiber surface modification strategies.

Fifield, Leonard S.; Huang, Cheng; Simmons, Kevin L.

2010-01-01

6

Use of natural particles for the removal of paint from aeronautical composite materials  

NASA Astrophysics Data System (ADS)

Paint removal by blasting and its effects on the surface morphology of aeronautical composite materials are investigated. An ideal combination of the parameters for mechanical paint removal by blasting such as particle type, size, velocity and angle of incidence yields a stripped aircraft skin substrate with minimal or no damage. Natural particles, specifically white corn flour, seem to be a good choice for paint removal by blasting. Since they are softer as well as smaller in size than other particles used for paint removal, they minimize the amount of damage to the surface of the composite. They are also cheaper and produce no harm to environment. The variation of the degree of surface roughness and the amount of broken fibers were correlated with some stripping parameters, such as particle impact angle and velocity. This defined an optimum environment for paint removal by blasting.

Guy, Thu-Ha; Lankarani, Hamid M.; Talia, Jorge E.

7

Cosmic ray interactions with lunar materials - Nature and composition of species formed  

NASA Technical Reports Server (NTRS)

The paper discusses the effect of cosmic-ray proton interactions with lunar material, the nature and composition of the species resulting from these interactions, and the contribution of these species to the lunar atmosphere. It is shown that hydrogen atoms resulting from cosmic-ray proton neutralization escape into the atmosphere mostly as H2, that only a small fraction of the very small amount of OH and H2O produced by cosmic-ray protons escapes into the atmosphere, and that cosmic-ray protons play a very minor role, as compared with solar-wind protons, in producing lunar atmospheric hydrogen and hydrogenated species. It is concluded that the atmospheric contributions of H2, H, OH, and H2O produced by cosmic-ray protons are about three orders of magnitude less than those due to solar-wind protons.

Mukherjee, N. R.

1976-01-01

8

Composite structural materials  

NASA Technical Reports Server (NTRS)

Various topics relating to composite structural materials for use in aircraft structures are discussed. The mechanical properties of high performance carbon fibers, carbon fiber-epoxy interface bonds, composite fractures, residual stress in high modulus and high strength carbon fibers, fatigue in composite materials, and the mechanical properties of polymeric matrix composite laminates are among the topics discussed.

Loewy, R. G.; Wiberley, S. E.

1985-01-01

9

Preparation of antibacterial composite material of natural rubber particles coated with silica and titania  

NASA Astrophysics Data System (ADS)

Silica coating, followed by titania coating, was performed over spray-dried natural rubber (NR) compound for physical and anti-bacterial characterizations. Titania has a strong photo-oxidative catalytic property, which can disinfect bacteria, but may degrade NR. Therefore, silica coating was intended to form a barrier between NR and titania. First, NR particles were prepared by spray-drying of NR compound latex, formulated for household glove products, mixed with sodium dodecyl sulfate (SDS) to reduce particle agglomeration. The factorial experimental design was employed to investigate the effects of nozzle flow rate (500-700 Lh-1), inlet air temperature (110-150 °C), SDS content (35-55 phr) and mass flow rate (1.2-1.7 g rubber/min) on NR yield and moisture content. Then, the NR compound particles prepared at the optimum condition were coated with silica, using tetraethoxysilane (TEOS) as the precursor, by chemical vapor deposition (CVD) at 60 °C for 2-48 hours. Next, the particles were coated with titania using titanium tetrafluoride (TiF4) by liquid phase deposition (LPD) at 60 ºC for 4-8 hours. The NR composites were characterized for surface morphology by SEM, silica and titania content by TGA and EDX. The NR composites were found to cause more than 99% reduction of Escherichia coli and Staphylococcus aureus under 1-hour exposure to natural light.

Wisutiratanamanee, Apisit; Poompradub, Sirilux; Poochinda, Kunakorn

2014-06-01

10

Tough Composite Materials  

NASA Technical Reports Server (NTRS)

Papers and working group summaries are presented which address composite material behavior and performance improvement. Topic areas include composite fracture toughness and impact characterization, constituent properties and interrelationships, and matrix synthesis and characterization.

Vosteen, L. F. (compiler); Johnson, N. J. (compiler); Teichman, L. A. (compiler)

1984-01-01

11

Acceleration and localization of subcritical crack growth in a natural composite material.  

PubMed

Catastrophic failure of natural and engineered materials is often preceded by an acceleration and localization of damage that can be observed indirectly from acoustic emissions (AE) generated by the nucleation and growth of microcracks. In this paper we present a detailed investigation of the statistical properties and spatiotemporal characteristics of AE signals generated during triaxial compression of a sandstone sample. We demonstrate that the AE event amplitudes and interevent times are characterized by scaling distributions with shapes that remain invariant during most of the loading sequence. Localization of the AE activity on an incipient fault plane is associated with growth in AE rate in the form of a time-reversed Omori law with an exponent near 1. The experimental findings are interpreted using a model that assumes scale-invariant growth of the dominating crack or fault zone, consistent with the Dugdale-Barenblatt "process zone" model. We determine formal relationships between fault size, fault growth rate, and AE event rate, which are found to be consistent with the experimental observations. From these relations, we conclude that relatively slow growth of a subcritical fault may be associated with a significantly more rapid increase of the AE rate and that monitoring AE rate may therefore provide more reliable predictors of incipient failure than direct monitoring of the growing fault. PMID:25493797

Lennartz-Sassinek, S; Main, I G; Zaiser, M; Graham, C C

2014-11-01

12

Acceleration and localization of subcritical crack growth in a natural composite material  

NASA Astrophysics Data System (ADS)

Catastrophic failure of natural and engineered materials is often preceded by an acceleration and localization of damage that can be observed indirectly from acoustic emissions (AE) generated by the nucleation and growth of microcracks. In this paper we present a detailed investigation of the statistical properties and spatiotemporal characteristics of AE signals generated during triaxial compression of a sandstone sample. We demonstrate that the AE event amplitudes and interevent times are characterized by scaling distributions with shapes that remain invariant during most of the loading sequence. Localization of the AE activity on an incipient fault plane is associated with growth in AE rate in the form of a time-reversed Omori law with an exponent near 1. The experimental findings are interpreted using a model that assumes scale-invariant growth of the dominating crack or fault zone, consistent with the Dugdale-Barenblatt "process zone" model. We determine formal relationships between fault size, fault growth rate, and AE event rate, which are found to be consistent with the experimental observations. From these relations, we conclude that relatively slow growth of a subcritical fault may be associated with a significantly more rapid increase of the AE rate and that monitoring AE rate may therefore provide more reliable predictors of incipient failure than direct monitoring of the growing fault.

Lennartz-Sassinek, S.; Main, I. G.; Zaiser, M.; Graham, C. C.

2014-11-01

13

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

Clough, R.L.; Sylwester, A.P.

1989-05-23

14

Composite structural materials  

NASA Technical Reports Server (NTRS)

Overall emphasis is on basic long-term research in the following categories: constituent materials, composite materials, generic structural elements, processing science technology; and maintaining long-term structural integrity. Research in basic composition, characteristics, and processing science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to present and future problems. Detailed descriptions of the progress achieved in the various component parts of this comprehensive program are presented.

Loewy, R.; Wiberley, S. E.

1986-01-01

15

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

Clough, R.L.; Sylwester, A.P.

1988-06-20

16

Composite structural materials  

NASA Technical Reports Server (NTRS)

The development and application of composite materials to aerospace vehicle structures which began in the mid 1960's has now progressed to the point where what can be considered entire airframes are being designed and built using composites. Issues related to the fabrication of non-resin matrix composites and the micro, mezzo and macromechanics of thermoplastic and metal matrix composites are emphasized. Several research efforts are presented. They are entitled: (1) The effects of chemical vapor deposition and thermal treatments on the properties of pitch-based carbon fiber; (2) Inelastic deformation of metal matrix laminates; (3) Analysis of fatigue damage in fibrous MMC laminates; (4) Delamination fracture toughness in thermoplastic matrix composites; (5) Numerical investigation of the microhardness of composite fracture; and (6) General beam theory for composite structures.

Loewy, Robert G.; Wiberley, Stephen E.

1987-01-01

17

Direct composite restorative materials.  

PubMed

Composite dental restorative materials have advanced considerably over the past 10 years. Although composites have not totally replaced amalgam, they have become a viable substitute in many situations. Problems still exist with polymerization contraction stress, large differences in the coefficient of thermal expansion (CTE) of composites compared with tooth structure, and with some technique sensitivity; however, new expanding resins, nanofiller technology, and improved bonding systems have the potential to reduce these problems. With increased patient demands for esthetic restorations, the use of direct filling composite materials will continue to grow. The one major caveat to this prediction is that clinicians must continue to use sound judgment on when, where, and how to use composite restoratives in their practices. PMID:17586149

Puckett, Aaron D; Fitchie, James G; Kirk, Pia Chaterjee; Gamblin, Jefferson

2007-07-01

18

Nanostructured composite reinforced material  

DOEpatents

A family of materials wherein nanostructures and/or nanotubes are incorporated into a multi-component material arrangement, such as a metallic or ceramic alloy or composite/aggregate, producing a new material or metallic/ceramic alloy. The new material has significantly increased strength, up to several thousands of times normal and perhaps substantially more, as well as significantly decreased weight. The new materials may be manufactured into a component where the nanostructure or nanostructure reinforcement is incorporated into the bulk and/or matrix material, or as a coating where the nanostructure or nanostructure reinforcement is incorporated into the coating or surface of a "normal" substrate material. The nanostructures are incorporated into the material structure either randomly or aligned, within grains, or along or across grain boundaries.

Seals, Roland D. (Oak Ridge, TN); Ripley, Edward B. (Knoxville, TN); Ludtka, Gerard M. (Oak Ridge, TN)

2012-07-31

19

Modified Composite Materials Workshop  

NASA Technical Reports Server (NTRS)

The reduction or elimination of the hazard which results from accidental release of graphite fibers from composite materials was studied at a workshop. At the workshop, groups were organized to consider six topics: epoxy modifications, epoxy replacement, fiber modifications, fiber coatings and new fibers, hybrids, and fiber release testing. Because of the time required to develop a new material and acquire a design data base, most of the workers concluded that a modified composite material would require about four to five years of development and testing before it could be applied to aircraft structures. The hybrid working group considered that some hybrid composites which reduce the risk of accidental fiber release might be put into service over the near term. The fiber release testing working group recommended a coordinated effort to define a suitable laboratory test.

Dicus, D. L. (compiler)

1978-01-01

20

Material Transfer of Composite Contact Materials  

Microsoft Academic Search

Composite technology provides very promising possibilities of improving one property of a given material without changing the other for the worse. The material transfer behavior of some fiber composite materials like AgNi and CuPd has been studied. Fiber composite contact materials can be fabricated in a simple and thus inexpensive way by bundling and simultaneous deformation of clad wires. It

HANS H. KOCHER; D. Stockel

1979-01-01

21

Composite materials: Testing and design  

NASA Technical Reports Server (NTRS)

The present conference discusses topics in the analysis of composite structures, composite materials' impact and compression behavior, composite materials characterization methods, composite failure mechanisms, NDE methods for composites, and filament-wound and woven composite materials' fabrication. Attention is given to the automated design of a composite plate for damage tolerance, the effects of adhesive layers on composite laminate impact damage, instability-related delamination growth in thermoset and thermoplastic composites, a simple shear fatigue test for unidirectional E-glass epoxy, the growth of elliptic delaminations in laminates under cyclic transverse shear, and the mechanical behavior of braided composite materials.

Whitcomb, John D. (editor)

1988-01-01

22

Tough composite materials: Recent developments  

SciTech Connect

A series of studies on tough composite materials is presented in this book. These composite materials are strong, but lightweight; and they are being used as metal replacements in applications where weight reduction is important. The material covered here provides an overview of NASA and other research aimed at improving composite material performance and increasing the understanding of composite material behavior. The book covers composite fracture toughness and impact characterization, constituent properties and interrelationships, matrix synthesis and characterization, and selected additional subjects.

Not Available

1985-01-01

23

Aerogel/polymer composite materials  

NASA Technical Reports Server (NTRS)

The invention provides new composite materials containing aerogels blended with thermoplastic polymer materials at a weight ratio of aerogel to thermoplastic polymer of less than 20:100. The composite materials have improved thermal insulation ability. The composite materials also have better flexibility and less brittleness at low temperatures than the parent thermoplastic polymer materials.

Williams, Martha K. (Inventor); Smith, Trent M. (Inventor); Fesmire, James E. (Inventor); Roberson, Luke B. (Inventor); Clayton, LaNetra M. (Inventor)

2010-01-01

24

Composite electric contact materials  

NASA Astrophysics Data System (ADS)

Two-phase composite materials, i.e., a high-melting component combined with a material exhibiting good electrical and thermal properties find a wide range of application for the manufacture of small- and medium-load relays and switches. Composite contacts can be used in air circuit-breakers (W-Ag, Ag-Ni), oil circuit-breakers (W-Cu, Mo-Cn), vacuum-type switches (W-CuSb, CuCr), and also switches operating in an atmosphere of SF sub 6 (W-Cu). Present-day trends aimed at increasing operating reliability and extending the service life of electrical equipment are finding their expression in efforts being made to modify the classical composites with a veiw to imparting new properties to them by suitably changing their composition and structure. These trends are also aimed at reducing the consumption of noble metals and of strategically important ones. Modern materials engineering and metallurgical technologies are being used, including isostatic sintering or explosive forming. Owing to the high activity of the constituents, all processes are conducted under high vacuum or in pure reducing atmospheres.

Senkara, J.; Kowalczyk, J.

1985-12-01

25

Advanced composite materials and processes  

NASA Technical Reports Server (NTRS)

Composites are generally defined as two or more individual materials, which, when combined into a single material system, results in improved physical and/or mechanical properties. The freedom of choice of the starting components for composites allows the generation of materials that can be specifically tailored to meet a variety of applications. Advanced composites are described as a combination of high strength fibers and high performance polymer matrix materials. These advanced materials are required to permit future aircraft and spacecraft to perform in extended environments. Advanced composite precursor materials, processes for conversion of these materials to structures, and selected applications for composites are reviewed.

Baucom, Robert M.

1991-01-01

26

Short courses in Composite Materials  

E-print Network

manufacturing techniques will continue to advance mechanical design. The influence of these technologies such advanced materials is the change in process and behaviours required to design and manufacture composites to composite materials technology, or indeed individuals who would like to understand how composite materials

Davies, John N.

27

Processing composite materials  

NASA Technical Reports Server (NTRS)

The fabrication of several composite structural articles including DC-10 upper aft rudders, L-1011 vertical fins and composite biomedical appliances are discussed. Innovative composite processing methods are included.

Baucom, R. M.

1982-01-01

28

Generalized Compositions of Natural Numbers  

E-print Network

We consider compositions of natural numbers when there are different types of each natural number. Several recursions as well as some closed formulas for the number of compositions is derived. We also find its relationships with some known classes of integers such as Fibonacci, Catalan, Pell, Pell-Lucas, and Jacobsthal numbers.

Janjic, Milan

2010-01-01

29

Natural Fiber Composites: A Review  

SciTech Connect

The need for renewable fiber reinforced composites has never been as prevalent as it currently is. Natural fibers offer both cost savings and a reduction in density when compared to glass fibers. Though the strength of natural fibers is not as great as glass, the specific properties are comparable. Currently natural fiber composites have two issues that need to be addressed: resin compatibility and water absorption. The following preliminary research has investigated the use of Kenaf, Hibiscus cannabinus, as a possible glass replacement in fiber reinforced composites.

Westman, Matthew P.; Fifield, Leonard S.; Simmons, Kevin L.; Laddha, Sachin; Kafentzis, Tyler A.

2010-03-07

30

Natural Fiber or Glass Reinforced Polypropylene Composites?  

NASA Astrophysics Data System (ADS)

Problems related to the recycle of conventional composite materials are becoming always more relevant for many industrial fields. Natural fiber composites (NFC) have recently gained much attention due to their low cost, environmental gains (eco-compatibility), easy disposal, reduction in volatile organic emissions, and their potential to compete with glass fiber composites (GFC). Interest in natural fibers is not only based over ecological aspects. NFC have good mechanical performances in relation to their low specific weight and low price. A characterization of mechanical properties, dynamic behavior, and moisture absorption is presented.

Lorenzi, W.; Di Landro, L.; Casiraghi, A.; Pagano, M. R.

2008-08-01

31

Reversibly assembled cellular composite materials.  

PubMed

We introduce composite materials made by reversibly assembling a three-dimensional lattice of mass-produced carbon fiber-reinforced polymer composite parts with integrated mechanical interlocking connections. The resulting cellular composite materials can respond as an elastic solid with an extremely large measured modulus for an ultralight material (12.3 megapascals at a density of 7.2 milligrams per cubic centimeter). These materials offer a hierarchical decomposition in modeling, with bulk properties that can be predicted from component measurements and deformation modes that can be determined by the placement of part types. Because site locations are locally constrained, structures can be produced in a relative assembly process that merges desirable features of fiber composites, cellular materials, and additive manufacturing. PMID:23950496

Cheung, Kenneth C; Gershenfeld, Neil

2013-09-13

32

Soft magnetic composite materials (SMCs)  

Microsoft Academic Search

Soft magnetic composites (SMCs), which are used in electromagnetic applications, can be described as ferromagnetic powder particles surrounded by an electrical insulating film. SMC components are normally manufactured by conventional PM compaction combined with new techniques, such as two step compaction, warm compaction, multi-step and magnetic annealing followed by a heat treatment at relatively low temperature. These composite materials offer

H. Shokrollahi; K. Janghorban

2007-01-01

33

Ultrasonic stress wave characterization of composite materials  

NASA Technical Reports Server (NTRS)

The work reported covers three simultaneous projects. The first project was concerned with: (1) establishing the sensitivity of the acousto-ultrasonic method for evaluating subtle forms of damage development in cyclically loaded composite materials, (2) establishing the ability of the acousto-ultrasonic method for detecting initial material imperfections that lead to localized damage growth and final specimen failure, and (3) characteristics of the NBS/Proctor sensor/receiver for acousto-ultrasonic evaluation of laminated composite materials. The second project was concerned with examining the nature of the wave propagation that occurs during acoustic-ultrasonic evaluation of composite laminates and demonstrating the role of Lamb or plate wave modes and their utilization for characterizing composite laminates. The third project was concerned with the replacement of contact-type receiving piezotransducers with noncontacting laser-optical sensors for acousto-ultrasonic signal acquisition.

Duke, J. C., Jr.; Henneke, E. G., II; Stinchcomb, W. W.

1986-01-01

34

Soft magnetic composites-materials and applications  

Microsoft Academic Search

The group of soft magnetic composites (SMCs) have expanded by the introduction of new materials with significantly improved low-medium frequency properties, which has made SMCs a viable alternative to steel laminations in a range of new applications, such as rotating machinery, sensors and fast switching solenoids. SMC components are successfully manufactured using the powder metallurgy compaction process. The isotropic nature

L. O. Hultman; A. G. Jack

2003-01-01

35

Nanophase and Composite Optical Materials  

NASA Technical Reports Server (NTRS)

This talk will focus on accomplishments, current developments, and future directions of our work on composite optical materials for microgravity science and space exploration. This research spans the order parameter from quasi-fractal structures such as sol-gels and other aggregated or porous media, to statistically random cluster media such as metal colloids, to highly ordered materials such as layered media and photonic bandgap materials. The common focus is on flexible materials that can be used to produce composite or artificial materials with superior optical properties that could not be achieved with homogeneous materials. Applications of this work to NASA exploration goals such as terraforming, biosensors, solar sails, solar cells, and vehicle health monitoring, will be discussed.

2003-01-01

36

Composite materials for space applications  

NASA Technical Reports Server (NTRS)

The objectives of the program were to: generate mechanical, thermal, and physical property test data for as-fabricated advanced materials; design and fabricate an accelerated thermal cycling chamber; and determine the effect of thermal cycling on thermomechanical properties and dimensional stability of composites. In the current program, extensive mechanical and thermophysical property tests of various organic matrix, metal matrix, glass matrix, and carbon-carbon composites were conducted, and a reliable database was constructed for spacecraft material selection. Material property results for the majority of the as-fabricated composites were consistent with the predicted values, providing a measure of consolidation integrity attained during fabrication. To determine the effect of thermal cycling on mechanical properties, microcracking, and thermal expansion behavior, approximately 500 composite specimens were exposed to 10,000 cycles between -150 and +150 F. These specimens were placed in a large (18 cu ft work space) thermal cycling chamber that was specially designed and fabricated to simulate one year low earth orbital (LEO) thermal cycling in 20 days. With this rate of thermal cycling, this is the largest thermal cycling unit in the country. Material property measurements of the thermal cycled organic matrix composite laminate specimens exhibited less than 24 percent decrease in strength, whereas, the remaining materials exhibited less than 8 percent decrease in strength. The thermal expansion response of each of the thermal cycled specimens revealed significant reduction in hysteresis and residual strain, and the average CTE values were close to the predicted values.

Rawal, Suraj P.; Misra, Mohan S.; Wendt, Robert G.

1990-01-01

37

Composite material impregnation unit  

NASA Technical Reports Server (NTRS)

This memorandum presents an introduction to the NASA multi-purpose prepregging unit which is now installed and fully operational at the Langley Research Center in the Polymeric Materials Branch. A description of the various impregnation methods that are available to the prepregger are presented. Machine operating details and protocol are provided for its various modes of operation. These include, where appropriate, the related equations for predicting the desired prepreg specifications. Also, as the prepregger is modular in its construction, each individual section is described and discussed. Safety concerns are an important factor and a chapter has been included that highlights the major safety features. Initial experiences and observations for fiber impregnation are described. These first observations have given great insight into the areas of future work that need to be addressed. Future memorandums will focus on these individual processes and their related problems.

Wilkinson, S. P.; Marchello, J. M.; Johnston, N. J.

1993-01-01

38

Delamination growth in composite materials  

NASA Technical Reports Server (NTRS)

Research related to growth of an imbedded through-width delamination (ITWD) in a compression loaded composite structural element is presented. Composites with widely different interlaminar fracture resistance were examined, viz., graphite/epoxy (CYCOM 982) and graphite/PEEK (APC-2). The initial part of the program consisted of characterizing the material in tension, compression and shear mainly to obtain consistent material properties for analysis, but also as a check of the processing method developed for the thermoplastic APC-2 material. The characterization of the delamination growth in the ITWD specimen, which for the unidirectional case is essentially a mixed Mode 1 and 2 geometry, requires verified mixed-mode growth criteria for the two materials involved. For this purpose the main emphasis during this part of the investigation was on Mode 1 and 2 fracture specimens, namely the Double Cantilever Beam (DCB) and End Notched Flexure (ENF) specimens.

Gillespie, J. W., Jr.; Carlson, L. A.; Pipes, R. B.; Rothschilds, R.; Trethewey, B.; Smiley, A.

1985-01-01

39

Predicting Properties Of Composite Materials  

NASA Technical Reports Server (NTRS)

Micromechanical Combined Stress Analysis (MICSTRAN) computer code provides materials engineers with easy-to-use personal-computer-based software tool to calculate overall properties of composite, given properties of fibers and matrix. Computes overall thermoelastic parameters and stresses by micromechanical analysis. Written in FORTRAN 77.

Naik, Rajiv A.

1994-01-01

40

Aeroelastic tailoring of composite materials  

E-print Network

LIST OF FIGURES IiiTRODUCTI ON ST!!UCTURAL RESPONSE Deformation of Uniformly Stressed Isotropic and Anisotropic Plates Characterization of Composite Laminates . Effect of Material Parameters APPLICATIONS Aircraft Propellers Ship Propell rs... Aircraft Wings and Stabilizers Static Aeroelasticity Dynamic Aeroelasticity . Aeroelastic Tailoring SPECIAL TOPICS The Effects of Time, Tc?. perature, iio'. sture and Fa!:ic!ue Time Dependent Behavior Fatigue Residual Stresses Due to the Cure Cycle...

Rogers, Jesse Byron

2012-06-07

41

Improved Silica Aerogel Composite Materials  

NASA Technical Reports Server (NTRS)

A family of aerogel-matrix composite materials having thermal-stability and mechanical- integrity properties better than those of neat aerogels has been developed. Aerogels are known to be excellent thermal- and acoustic-insulation materials because of their molecular-scale porosity, but heretofore, the use of aerogels has been inhibited by two factors: (1) Their brittleness makes processing and handling difficult. (2) They shrink during production and shrink more when heated to high temperatures during use. The shrinkage and the consequent cracking make it difficult to use them to encapsulate objects in thermal-insulation materials. The underlying concept of aerogel-matrix composites is not new; the novelty of the present family of materials lies in formulations and processes that result in superior properties, which include (1) much less shrinkage during a supercritical-drying process employed in producing a typical aerogel, (2) much less shrinkage during exposure to high temperatures, and (3) as a result of the reduction in shrinkage, much less or even no cracking.

Paik, Jong-Ah; Sakamoto, Jeffrey; Jones, Steven

2008-01-01

42

NDE of polymeric composite material bridge components  

NASA Astrophysics Data System (ADS)

Rapid advancements with respect to utilization of polymeric composite materials for bridge components is occurring. This situation is driven primarily by the potential improvements offered by these materials with respect to long term durability. However, because of the developmental nature of these materials much of the materials characterization has involved short term testing without the synergistic effects of environmental exposure. Efforts to develop nondestructive evaluation procedures, essential for any wide spread use in critical structural applications, have been consequently limited. This paper discuses the effort to develop NDE methods for field inspection of hybrid glass and carbon fiber reinforced vinyl ester pultruded 'double box' I beams that are installed in a small bridge over Tom's Creek, in Blacksburg, Virginia. Integrated structural element sensors, dormant infrared devices, as well as acousto-ultrasonic methods are under development for detecting and monitoring the occurrence and progression of life limiting deterioration mechanisms.

Duke, John C., Jr.; Horne, Michael R.

1998-03-01

43

ULTRASONIC CHARACTERIZATION OF ADVANCED COMPOSITE MATERIALS  

Microsoft Academic Search

With increased use of composite materials in critical structural applications it is more important than ever to independently assure structural integrity. Complexity of the advanced composite materials including layered and bonded structures represents challenges in developing optimized ultrasonic tests. Traditional ultrasonic NDT methods are inappropriate and often misleading when applied to anisotropic and nonhomogeneous composite materials. In advanced technology applications

B. Boro Djordjevic

44

Composite materials for thermal energy storage  

DOEpatents

The present invention discloses composite material for thermal energy storage based upon polyhydric alcohols, such as pentaerythritol, trimethylol ethane (also known as pentaglycerine), neopentyl glycol and related compounds including trimethylol propane, monoaminopentaerythritol, diamino-pentaerythritol and tris(hydroxymethyl)acetic acid, separately or in combinations, which provide reversible heat storage through crystalline phase transformations. These phase change materials do not become liquid during use and are in contact with at least one material selected from the group consisting of metals, carbon siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, porous rock, and mixtures thereof. Particulate additions, such as aluminum or graphite powders, as well as metal and carbon fibers can also be incorporated therein. Particulate and/or fibrous additions can be introduced into molten phase change materials which can then be cast into various shapes. After the phase change materials have solidified, the additions will remain dispersed throughout the matrix of the cast solid. The polyol is in contact with at least one material selected from the group consisting of metals, carbon siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, and mixtures thereof.

Benson, David K. (Golden, CO); Burrows, Richard W. (Conifer, CO); Shinton, Yvonne D. (Northglenn, CO)

1986-01-01

45

Fractal nature of humic materials  

SciTech Connect

Fractals are geometric representatives of strongly disordered systems whose structure is described by nonintegral dimensions. A fundamental tenet of fractal geometry is that disorder persists at any characterization scale-length used to describe the system. The nonintegral nature of these fractal dimensions is the result of the realization that a disordered system must possess more structural detail than an ordered system with classical dimensions of 1, 2, or 3 in order to accommodate this disorder within disorder.'' Thus from a fractal perspective, disorder is seen as an inherent characteristic of the system rather than as a perturbative phenomena forced upon it. Humic materials are organic substances that are formed by the profound alteration of organic matter in a natural environment. They can be operationally divided into 3 fractions; humic acid (soluble in base), fulvic acid (soluble in acid or base), and humin (insoluble in acid or base). Each of these fraction has been shown to be an extremely heterogeneous mixture. These mixtures have proven so intractable that they may represent the ultimate in molecular disorder. In fact, based on the characteristics that humic materials must possess in order to perform their functions in natural systems, it has been proposed that the fundamental chemical characteristic of a humic material is not a discrete chemical structure but a pronounced lack of order on a molecular level. If the fundamental chemical characteristic of a humic material is a strongly disordered nature, as has been proposed, then humic materials should be amenable to characterization by fractal geometry. The purpose of this paper is to test this hypothesis.

Rice, J.A. (South Dakota State Univ., Brookings, SD (United States). Dept. of Chemistry); Lin, J.S. (Oak Ridge National Lab., TN (United States))

1992-01-01

46

Fractal nature of humic materials  

SciTech Connect

Fractals are geometric representatives of strongly disordered systems whose structure is described by nonintegral dimensions. A fundamental tenet of fractal geometry is that disorder persists at any characterization scale-length used to describe the system. The nonintegral nature of these fractal dimensions is the result of the realization that a disordered system must possess more structural detail than an ordered system with classical dimensions of 1, 2, or 3 in order to accommodate this ``disorder within disorder.`` Thus from a fractal perspective, disorder is seen as an inherent characteristic of the system rather than as a perturbative phenomena forced upon it. Humic materials are organic substances that are formed by the profound alteration of organic matter in a natural environment. They can be operationally divided into 3 fractions; humic acid (soluble in base), fulvic acid (soluble in acid or base), and humin (insoluble in acid or base). Each of these fraction has been shown to be an extremely heterogeneous mixture. These mixtures have proven so intractable that they may represent the ultimate in molecular disorder. In fact, based on the characteristics that humic materials must possess in order to perform their functions in natural systems, it has been proposed that the fundamental chemical characteristic of a humic material is not a discrete chemical structure but a pronounced lack of order on a molecular level. If the fundamental chemical characteristic of a humic material is a strongly disordered nature, as has been proposed, then humic materials should be amenable to characterization by fractal geometry. The purpose of this paper is to test this hypothesis.

Rice, J.A. [South Dakota State Univ., Brookings, SD (United States). Dept. of Chemistry; Lin, J.S. [Oak Ridge National Lab., TN (United States)

1992-03-01

47

A new approach for modeling composite materials  

NASA Astrophysics Data System (ADS)

The increasing use of composite materials is due to their ability to tailor materials for special purposes, with applications evolving day by day. This is why predicting the properties of these systems from their constituents, or phases, has become so important. However, assigning macroscopical optical properties for these materials from the bulk properties of their constituents is not a straightforward task. In this research, we present a spectral analysis of three-dimensional random composite typical nanostructures using an Extension of the Discrete Dipole Approximation (E-DDA code), comparing different approaches and emphasizing the influences of optical properties of constituents and their concentration. In particular, we hypothesize a new approach that preserves the individual nature of the constituents introducing at the same time a variation in the optical properties of each discrete element that is driven by the surrounding medium. The results obtained with this new approach compare more favorably with the experiment than previous ones. We have also applied it to a non-conventional material composed of a metamaterial embedded in a dielectric matrix. Our version of the Discrete Dipole Approximation code, the EDDA code, has been formulated specifically to tackle this kind of problem, including materials with either magnetic and tensor properties.

Alcaraz de la Osa, R.; Moreno, F.; Saiz, J. M.

2013-03-01

48

Estimating Weibull parameters for composite materials.  

NASA Technical Reports Server (NTRS)

This paper deals with the statistical analysis of strength and fracture of materials in general, with application to fiber composites. The 'weakest link' model is considered in a fairly general form, and the resulting equations are demonstrated by using a Weibull distribution for flaws. This distribution appears naturally in a variety of problems, and therefore additional attention is devoted to analysis and statistical estimation connected with this distribution. Special working charts are included to facilitate interpretation of observed data and estimation of parameters. Implications of the size effect are considered for various kinds of flaw distributions. The paper describes failure and damage in a fiber-reinforced systems.

Robinson, E. Y.

1972-01-01

49

Composite materials for thermal energy storage  

DOEpatents

A composite material for thermal energy storage based upon polyhydric alcohols, such as pentaerythritol, trimethylol ethane (also known as pentaglycerine), neopentyl glycol and related compounds including trimethylol propane, monoaminopentaerythritol, diamino-pentaerythritol and tris(hydroxymethyl)acetic acid, separately or in combinations, which provide reversible heat storage through crystalline phase transformations. These PCM's do not become liquid during use and are in contact with at least one material selected from the group consisting of metals, carbon, siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, porous rock, and mixtures thereof. Particulate additions such as aluminum or graphite powders, as well as metal and carbon fibers can also be incorporated therein. Particulate and/or fibrous additions can be introduced into molten phase change materials which can then be cast into various shapes. After the phase change materials have solidified, the additions will remain dispersed throughout the matrix of the cast solid. The polyol is in contact with at least one material selected from the group consisting of metals, carbon, siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, and mixtures thereof.

Benson, D.K.; Burrows, R.W.; Shinton, Y.D.

1985-01-04

50

Delamination growth in composite materials  

NASA Technical Reports Server (NTRS)

The Double Cantilever Beam (DCB) and the End Notched Flexure (ENF) specimens are employed to characterize MODE I and MODE II interlaminar fracture resistance of graphite/epoxy (CYCOM 982) and graphite/PEEK (APC2) composites. Sizing of test specimen geometries to achieve crack growth in the linear elastic regime is presented. Data reduction schemes based upon beam theory are derived for the ENF specimen and include the effects of shear deformation and friction between crack surfaces on compliance, C, and strain energy release rate, G sub II. Finite element (FE) analyses of the ENF geometry including the contact problem with friction are presented to assess the accuracy of beam theory expressions for C and G sub II. Virtual crack closure techniques verify that the ENF specimen is a pure Mode II test. Beam theory expressions are shown to be conservative by 20 to 40 percent for typical unidirectional test specimen geometries. A FE parametric study investigating the influence of delamination length and depth, span, thickness and material properties on G sub II is presented. Mode I and II interlaminar fracture test results are presented. Important experimental parameters are isolated, such as precracking techniques, rate effects, and nonlinear load-deflection response. It is found that subcritical crack growth and inelastic materials behavior, responsible for the observed nonlinearities, are highly rate-dependent phenomena with high rates generally leading to linear elastic response.

Gillespie, J. W., Jr.; Carlsson, L. A.; Pipes, R. B.; Rothschilds, R.; Trethewey, B.; Smiley, A.

1986-01-01

51

Composite materials for space structures  

NASA Technical Reports Server (NTRS)

The use of advanced composites for space structures is reviewed. Barriers likely to limit further applications of composites are discussed and highlights of research to improve composites are presented. Developments in composites technology which could impact spacecraft systems are reviewed to identify technology needs and opportunities.

Tenney, D. R.; Sykes, G. F.; Bowles, D. E.

1985-01-01

52

Optimized adhesives for strong, lightweight, damage-resistant, nanocomposite materials: new insights from natural materials  

NASA Astrophysics Data System (ADS)

From our investigations of natural composite materials such as abalone shell and bone we have learned the following. (1) Nature is frugal with resources: it uses just a few per cent glue, by weight, to glue together composite materials. (2) Nature does not avoid voids. (3) Nature makes optimized glues with sacrificial bonds and hidden length. We discuss how optimized adhesives combined with high specific stiffness/strength structures such as carbon nanotubes or graphene sheets could yield remarkably strong, lightweight, and damage-resistant materials.

Hansma, P. K.; Turner, P. J.; Ruoff, R. S.

2007-01-01

53

Nonlinear Dynamic Properties of Layered Composite Materials  

SciTech Connect

We present an application of the asymptotic homogenization method to study wave propagation in a one-dimensional composite material consisting of a matrix material and coated inclusions. Physical nonlinearity is taken into account by considering the composite's components as a Murnaghan material, structural nonlinearity is caused by the bonding condition between the components.

Andrianov, Igor V.; Topol, Heiko; Weichert, Dieter [Institute of General Mechanics, RWTH Aachen University, Termplergraben 64, Aachen, D-52062 (Germany); Danishevs'kyy, Vladyslav V. [Prydniprovs'ka State Academy of Civil Engineering and Architecture, Dnipropetrovs'k, Chernishevs'kogo 24a, UA-49600 (Ukraine)

2010-09-30

54

Method for machining holes in composite materials  

NASA Technical Reports Server (NTRS)

A method for boring well defined holes in a composite material such as graphite/epoxy is discussed. A slurry of silicon carbide powder and water is projected onto a work area of the composite material in which a hole is to be bored with a conventional drill bit. The silicon carbide powder and water slurry allow the drill bit, while experiencing only normal wear, to bore smooth, cylindrical holes in the composite material.

Daniels, Julia G. (inventor); Ledbetter, Frank E., III (inventor); Clemons, Johnny M. (inventor); Penn, Benjamin G. (inventor); White, William T. (inventor)

1987-01-01

55

NASA technology utilization survey on composite materials  

NASA Technical Reports Server (NTRS)

NASA and NASA-funded contractor contributions to the field of composite materials are surveyed. Existing and potential non-aerospace applications of the newer composite materials are emphasized. Economic factors for selection of a composite for a particular application are weight savings, performance (high strength, high elastic modulus, low coefficient of expansion, heat resistance, corrosion resistance,), longer service life, and reduced maintenance. Applications for composites in agriculture, chemical and petrochemical industries, construction, consumer goods, machinery, power generation and distribution, transportation, biomedicine, and safety are presented. With the continuing trend toward further cost reductions, composites warrant consideration in a wide range of non-aerospace applications. Composite materials discussed include filamentary reinforced materials, laminates, multiphase alloys, solid multiphase lubricants, and multiphase ceramics. New processes developed to aid in fabrication of composites are given.

Leeds, M. A.; Schwartz, S.; Holm, G. J.; Krainess, A. M.; Wykes, D. M.; Delzell, M. T.; Veazie, W. H., Jr.

1972-01-01

56

Improved Damage Resistant Composite Materials Incorporating Shape Memory Alloys  

NASA Technical Reports Server (NTRS)

Metallic shape memory alloys (SMA) such as nitinol have unique shape recovery behavior and mechanical properties associated with a material phase change that have been used in a variety of sensing and actuation applications. Recent studies have shown that integrating nitinol-SMA actuators into composite materials increases the composite material's functionality. Hybrid composites of conventional graphite/epoxy or glass/epoxy and nitinol-SMA elements can perform functions in applications where monolithic composites perform inadequately. One such application is the use of hybrid composites to function both in load bearing and armor capacities. While monolithic composites with high strength-to-weight ratios function efficiently as loadbearing structures, because of their brittle nature, impact loading can cause significant catastrophic damage. Initial composite failure modes such as delamination and matrix cracking dissipate some impact energy, but when stress exceeds the composite's ultimate strength, fiber fracture and material perforation become dominant. One of the few methods that has been developed to reduce material perforation is hybridizing polymer matrix composites with tough kevlar or high modulus polyethynylene plies. The tough fibers increase the impact resistance and the stiffer and stronger graphite fibers carry the majority of the load. Similarly, by adding nitinol-SMA elements that absorb impact energy through the stress-induced martensitic phase transformation, the composites' impact perforation resistance can be greatly enhanced. The results of drop-weight and high velocity gas-gun impact testing of various composite materials will be presented. The results demonstrate that hybridizing composites with nitinol-SMA elements significantly increases perforation resistance compared to other traditional toughening elements. Inspection of the composite specimens at various stages of perforation by optical microscope illustrates the mechanisms by which perforation is initiated. Results suggest that the out-of-plane transverse shear properties of the composite and nitinol elements have a significant effect on the perforation resistance. Applications that can utilize the hybrid composites effectively will also be presented with the experimental studies.

Paine, Jeffrey S. N.; Rogers, Craig A.

1996-01-01

57

Composite materials in dynamic shipboard structural mounts  

E-print Network

The purpose of this thesis is to investigate the viability of replacing traditional metal structural and machinery mounts with padding made of composite material. The two types of padding or isolation materials are represented ...

Faulk, Joanna (Joanna E.)

2011-01-01

58

Damage and fracture mechanics of composite materials  

Microsoft Academic Search

The design of structural systems in the aerospace industry has been characterized by a continuing search for strong, yet lightweight, materials to achieve maximum payload capability for minimum weight. In recent years, this search has led to a wide use of fiber reinforced composites, such as carbon, glass and kevelar based composites. Comparison of these new materials with the traditional

Saleh Ramadan Abdussalam

1999-01-01

59

Hysteresis losses in soft magnetic composite materials  

Microsoft Academic Search

Purpose – To analyze the Jiles and Atherton hysteresis model used for hysteresis losses estimation in soft magnetic composite (SMC) material. Design\\/methodology\\/approach – The Jiles and Atherton hysteresis model parameters are optimized with genetic algorithms (GAs) according to measured symmetric hysteresis loop of soft magnetic composite material. To overcome the uncertainty, finding the best-optimized parameters in a wide predefined searching

Bogomir Zidari?; Mykhaylo Zagirnyak; Konrad Lenasi; Damijan Miljavec

2006-01-01

60

Composite materials and method of making  

DOEpatents

A method for forming improved composite materials using a thermosetting polyester urethane hybrid resin, a closed cavity mold having an internal heat transfer mechanism used in this method, and the composite materials formed by this method having a hybrid of a carbon fiber layer and a fiberglass layer.

Simmons, Kevin L [Kennewick, WA; Wood, Geoffrey M [North Saanich, CA

2011-05-17

61

Ultrasonic Inspection Of Composite-Material Paraboloid  

NASA Technical Reports Server (NTRS)

Ultrasonic imaging system scanning three-dimensional curved surfaces developed. In original application, system used to determine integrity of composite-material paraboloidal reflector and its supporting structure. System also used to inspect composite-material structures with curved surfaces other than paraboloids, provided surfaces describable by mathematical functions. Position and orientation of transducer adjusted continuously to maintain normal incidence.

Chern, E. James

1994-01-01

62

Composite, nanostructured, super-hydrophobic material  

DOEpatents

A hydrophobic disordered composite material having a protrusive surface feature includes a recessive phase and a protrusive phase, the recessive phase having a higher susceptibility to a preselected etchant than the protrusive phase, the composite material having an etched surface wherein the protrusive phase protrudes from the surface to form a protrusive surface feature, the protrusive feature being hydrophobic.

D'Urso, Brian R. (Clinton, TN); Simpson, John T. (Clinton, TN)

2007-08-21

63

Natural materials for carbon capture.  

SciTech Connect

Naturally occurring clay minerals provide a distinctive material for carbon capture and carbon dioxide sequestration. Swelling clay minerals, such as the smectite variety, possess an aluminosilicate structure that is controlled by low-charge layers that readily expand to accommodate water molecules and, potentially, carbon dioxide. Recent experimental studies have demonstrated the efficacy of intercalating carbon dioxide in the interlayer of layered clays but little is known about the molecular mechanisms of the process and the extent of carbon capture as a function of clay charge and structure. A series of molecular dynamics simulations and vibrational analyses have been completed to assess the molecular interactions associated with incorporation of CO2 in the interlayer of montmorillonite clay and to help validate the models with experimental observation.

Myshakin, Evgeniy M. (National Energy Technology Laboratory, Pittsburgh, PA); Romanov, Vyacheslav N. (National Energy Technology Laboratory, Pittsburgh, PA); Cygan, Randall Timothy

2010-11-01

64

Composite materials for biomedical applications: a review.  

PubMed

The word "composite" refers to the combination, on a macroscopic scale, of two or more materials, different for composition, morphology and general physical properties. In many cases, and depending on the constituent properties, composites can be designed with a view to produce materials with properties tailored to fulfill specific chemical, physical or mechanical requirements. Therefore over the past 40 years the use of composites has progressively increased, and today composite materials have many different applications, i.e., aeronautic, automotive, naval, and so on. Consequently many composite biomaterials have recently been studied and tested for medical application. Some of them are currently commercialized for their advantages over traditional materials. Most human tissues such as bones, tendons, skin, ligaments, teeth, etc., are composites, made up of single constituents whose amount, distribution, morphology and properties determine the final behavior of the resulting tissue or organ. Man-made composites can, to some extent, be used to make prostheses able to mimic these biological tissues, to match their mechanical behavior and to restore the mechanical functions of the damaged tissue. Different types of composites that are already in use or are being investigated for various biomedical applications are presented in this paper. Specific advantages and critical issues of using composite biomaterials are also described (Journal of Applied Bio-materials & Biomechanics 2003; 1: 3-18). PMID:20803468

Salernitano, E; Migliaresi, C

2003-01-01

65

The nature of cometary materials  

NASA Technical Reports Server (NTRS)

Because cometary surfaces are likely to be far colder and of a different composition than planetary surfaces, there are some new considerations that must be examined in regards to placing instrumented packages or sample return devices on their surfaces. The qualitative analysis of the problem of attaching hardware to a comet and not being ejected back into space can be divided into two parts. The first problem is to pierce the mantle and obtain access to the icy core. Drilling through the mantle requires that the drilling forces be reacted. Reacting such forces probably requires attachment to the icy core below. Therefore, some kinetic impact piercing device is likely to be required as the first act of attachment. The second problem for a piercing device to overcome is the force produced by the impact kinetic energy that tries to eject the piercing device back into space. The mantle and icy core can absorb some of the impact kinetic energy in the form of fracture formation and friction energy. The energy that is not absorbed in these two ways is stored by the core as elastic deformation of the mantle and icy core. It is concluded that because the cometary materials are almost certainly brittle and the icy core is likely to be self lubricating, the elastic rebound and gas pressure expulsion forces must be counteracted by forces greater than those that may be provided by a piercing device or its capture devices (barbs).

Stephens, James

1989-01-01

66

Flame-retardant composite materials  

NASA Technical Reports Server (NTRS)

The properties of eight different graphite composite panels fabricated using four different resin matrices and two types of graphite reinforcement are described. The resin matrices included: VPSP/BMI, a blend of vinylpolystyryl pyridine and bismaleimide; BMI, a bismaleimide; and phenolic and PSP, a polystyryl pyridine. The graphite fiber used was AS-4 in the form of either tape or fabric. The properties of these composites were compared with epoxy composites. It was determined that VPSP/BMI with the graphite tape was the optimum design giving the lowest heat release rate.

Kourtides, Demetrius A.

1991-01-01

67

Advanced composites: Environmental effects on selected resin matrix materials  

NASA Technical Reports Server (NTRS)

The effects that expected space flight environment has upon the mechanical properties of epoxy and polyimide matrix composites were analyzed. Environmental phenomena covered water immersion, high temperature aging, humidity, lightning strike, galvanic action, electromagnetic interference, thermal shock, rain and sand erosion, and thermal/vacuum outgassing. The technology state-of-the-art for graphite and boron reinforced epoxy and polyimide matrix materials is summarized to determine the relative merit of using composites in the space shuttle program. Resin matrix composites generally are affected to some degree by natural environmental phenomena with polyimide resin matrix materials less affected than epoxies.

Welhart, E. K.

1976-01-01

68

Isotopic Compositions of Uranium Reference Materials  

NASA Astrophysics Data System (ADS)

Uranium isotopic compositions of a variety of U standard materials were measured at Lawrence Livermore National Laboratory and are reported here. Both thermal ionization mass spectrometry (TIMS) and multi-collector inductively couple plasma mass spectrometry (MC-ICPMS) were used to determine ratios of the naturally occurring isotopes of U. Establishing an internally coherent set of isotopic values for a range of U standards is essential for inter-laboratory comparison of small differences in 238U/235U, as well as the minor isotopes of U. Differences of ~1.3‰ are now being observed in 238U/235U in natural samples, and may play an important role in understanding U geochemistry where tracing the origin of U is aided by U isotopic compositions. The 238U/235U ratios were measured with a TRITON TIMS using a mixed 233U-236U isotopic tracer to correct for instrument fractionation. This tracer was extremely pure and resulted in only very minor corrections on the measured 238U/235U ratios of ~0.03. The values obtained for 238U/235U are: IRMM184 = 137.698 ± 0.020 (n=15), SRM950a = 137.870 ± 0.018 (n=8), and CRM112a = 137.866 ± 0.030 (n=16). Uncertainties represent 2 s.d. of the population. Our measured value for IRMM184 is in near-perfect agreement with the certified value of 137.697 ± 0.042. However, the U isotopic compositions of SRM950a and CRM112a are not certified. Minor isotopes of U were determined with a Nu Plasma HR MC-ICPMS and mass bias was corrected by sample/standard bracketing to IRMM184, using its certified 238U/235U ratio. Thus, the isotopic compositions determined using both instruments are compatible. The values obtained for 234U/235U are: SRM950a = (7.437 ± 0.043)x10-3 (n=18), and CRM112a = (7.281 ± 0.050)x10-3 (n=16), both of which are in good agreement with published values. The value for 236U/235U in SRM950a was determined to be (8.48 ± 2.63)x10-6, whereas 236U was not detected in CRM112a. We are currently obtaining the U isotopic composition of CRM129a. Preliminary results suggest that the 238U/235U ratio is within error, but slightly lower than the certified value of 137.71.

Jacobsen, B.; Borg, L. E.; Williams, R. W.; Brennecka, G.; Hutcheon, I. D.

2009-12-01

69

Materials research at Stanford University. [composite materials, crystal structure, acoustics  

NASA Technical Reports Server (NTRS)

Research activity related to the science of materials is described. The following areas are included: elastic and thermal properties of composite materials, acoustic waves and devices, amorphous materials, crystal structure, synthesis of metal-metal bonds, interactions of solids with solutions, electrochemistry, fatigue damage, superconductivity and molecular physics and phase transition kinetics.

1975-01-01

70

Ceramic composites: Enabling aerospace materials  

NASA Technical Reports Server (NTRS)

Ceramics and ceramic matrix composites (CMC) have the potential for significant impact on the performance of aerospace propulsion and power systems. In this paper, the potential benefits are discussed in broad qualitative terms and are illustrated by some specific application case studies. The key issues in need of resolution for the potential of ceramics to be realized are discussed.

Levine, S. R.

1992-01-01

71

Advanced composite materials for precision segmented reflectors  

NASA Technical Reports Server (NTRS)

The objective in the NASA Precision Segmented Reflector (PSR) project is to develop new composite material concepts for highly stable and durable reflectors with precision surfaces. The project focuses on alternate material concepts such as the development of new low coefficient of thermal expansion resins as matrices for graphite fiber reinforced composites, quartz fiber reinforced epoxies, and graphite reinforced glass. Low residual stress fabrication methods will be developed. When coupon specimens of these new material concepts have demonstrated the required surface accuracies and resistance to thermal distortion and microcracking, reflector panels will be fabricated and tested in simulated space environments. An important part of the program is the analytical modeling of environmental stability of these new composite materials concepts through constitutive equation development, modeling of microdamage in the composite matrix, and prediction of long term stability (including viscoelasticity). These analyses include both closed form and finite element solutions at the micro and macro levels.

Stein, Bland A.; Bowles, David E.

1988-01-01

72

Manufacturing technology of the composite materials: nanocrystalline material - polymer type  

Microsoft Academic Search

Purpose: This paper presents the material and technological solution which makes it possible to obtain the nanocrystalline, ferromagnetic powder material of Fe73.5Cu1Nb3Si13.5B9 alloy after its thermal nanocrystallization with the succeeding high-energy milling. Another aspect was to develop the technology to obtain the nanocrystalline composite materials made by binding the obtained powder material with the high density low- pressures polyethylene (PEHD)

B. Zi?bowicz; D. Szewieczek; L. A. Dobrza?ski

73

Composite Material Application to Liquid Rocket Engines  

NASA Technical Reports Server (NTRS)

The substitution of reinforced plastic composite (RPC) materials for metal was studied. The major objectives were to: (1) determine the extent to which composite materials can be beneficially used in liquid rocket engines; (2) identify additional technology requirements; and (3) determine those areas which have the greatest potential for return. Weight savings, fabrication costs, performance, life, and maintainability factors were considered. Two baseline designs, representative of Earth to orbit and orbit to orbit engine systems, were selected. Weight savings are found to be possible for selected components with the substitution of materials for metal. Various technology needs are identified before RPC material can be used in rocket engine applications.

Judd, D. C.

1982-01-01

74

NASA Thermographic Inspection of Advanced Composite Materials  

NASA Technical Reports Server (NTRS)

As the use of advanced composite materials continues to increase in the aerospace community, the need for a quantitative, rapid, in situ inspection technology has become a critical concern throughout the industry. In many applications it is necessary to monitor changes in these materials over an extended period of time to determine the effects of various load conditions. Additionally, the detection and characterization of defects such as delaminations, is of great concern. This paper will present the application of infrared thermography to characterize various composite materials and show the advantages of different heat source types. Finally, various analysis methodologies used for quantitative material property characterization will be discussed.

Cramer, K. Elliott

2004-01-01

75

Composite materials inspection. [ultrasonic vibration holographic NDT  

NASA Technical Reports Server (NTRS)

Investigation of the application requirements, advantages, and limitations of nondestructive testing by a technique of ultrasonic-vibration holographic-interferometry readout used in a production control facility for the inspection of a single product such as composite compressor blades. It is shown that, for the detection and characterization of disbonds in composite material structures, this technique may represent the most inclusive test method.

Erf, R. K.

1974-01-01

76

Acoustic emission monitoring of polymer composite materials  

NASA Technical Reports Server (NTRS)

The techniques of acoustic emission monitoring of polymer composite materials is described. It is highly sensitive, quasi-nondestructive testing method that indicates the origin and behavior of flaws in such materials when submitted to different load exposures. With the use of sophisticated signal analysis methods it is possible the distinguish between different types of failure mechanisms, such as fiber fracture delamination or fiber pull-out. Imperfections can be detected while monitoring complex composite structures by acoustic emission measurements.

Bardenheier, R.

1981-01-01

77

Method of making a composite refractory material  

DOEpatents

A composite refractory material is prepared by combining boron carbide with furan resin to form a mixture containing about 8 wt. % furan resin. The mixture is formed into a pellet which is placed into a grit pack comprising an oxide of an element such as yttrium to form a sinterable body. The sinterable body is sintered under vacuum with microwave energy at a temperature no greater than 2000 C to form a composite refractory material.

Morrow, M.S.; Holcombe, C.E.

1995-09-26

78

Method of making a composite refractory material  

DOEpatents

A composite refractory material is prepared by combining boron carbide with furan resin to form a mixture containing about 8 wt. % furan resin. The mixture is formed into a pellet which is placed into a grit pack comprising an oxide of an element such as yttrium to form a sinterable body. The sinterable body is sintered under vacuum with microwave energy at a temperature no greater than 2000.degree. C. to form a composite refractory material.

Morrow, Marvin S. (Kingston, TN); Holcombe, Cressie E. (Knoxville, TN)

1995-01-01

79

Method to fabricate layered material compositions  

DOEpatents

A new class of processes suited to the fabrication of layered material compositions is disclosed. Layered material compositions are typically three-dimensional structures which can be decomposed into a stack of structured layers. The best known examples are the photonic lattices. The present invention combines the characteristic features of photolithography and chemical-mechanical polishing to permit the direct and facile fabrication of, e.g., photonic lattices having photonic bandgaps in the 0.1-20.mu. spectral range.

Fleming, James G. (Albuquerque, NM); Lin, Shawn-Yu (Albuquerque, NM)

2002-01-01

80

Development and characterization of renewable resource- structural composite materials  

E-print Network

Cannabis sativa as reinforcement/filler of thermoplastic composite materials." Composites Part A: Applied ScienceCannabis sativa as reinforcement/filler of thermoplastic composite materials." Composites Part A: Applied Science

Cutter, Andrea Gillian

2008-01-01

81

Biomimicry of bamboo bast fiber with engineering composite materials  

Microsoft Academic Search

Bamboo, one of the strongest natural structural composite materials, has many distinguishing features. It has been found that its reinforcement unit, hollow, multilayered and spirally-wound bast fiber, plays an extremely important role in its mechanical behavior. In the present work, on the basis of the study on bamboo bast fiber and wood tracheid, a biomimetic model of the reinforcing element,

S. H. Li; Q. Y. Zeng; Y. L. Xiao; S. Y. Fu; B. L. Zhou

1995-01-01

82

Oxygen isotope composition of trinitite postdetonation materials.  

PubMed

Trinitite is the melt glass produced subsequent the first nuclear bomb test conducted on July 16, 1945, at White Sands Range (Alamagordo, NM). The geological background of the latter consists of arkosic sand that was fused with radioactive debris and anthropogenic materials at ground zero subsequent detonation of the device. Postdetonation materials from historic nuclear weapon test sites provide ideal samples for development of novel forensic methods for attribution and studying the chemical/isotopic effects of the explosion on the natural geological environment. In particular, the latter effects can be evaluated relative to their spatial distribution from ground zero. We report here ?(18)O(‰) values for nonmelted, precursor minerals phases (quartz, feldspar, calcite), "feldspathic-rich" glass, "average" melt glass, and bulk (natural) unmelted sand from the Trinity site. Prior to oxygen isotope analysis, grains/crystals were examined using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) to determine their corresponding major element composition. ?(18)O values for bulk trinitite samples exhibit a large range (11.2-15.5‰) and do not correlate with activity levels for activation product (152)Eu; the latter levels are a function of their spatial distribution relative to ground zero. Therefore, the slow neutron flux associated with the nuclear explosion did not perturb the (18)O/(16)O isotope systematics. The oxygen isotope values do correlate with the abundances of major elements derived from precursor minerals present within the arkosic sand. Hence, the O isotope ratios documented here for trinitite melt glass can be attributed to a mixture of the respective signatures for precursor minerals at the Trinity site prior to the nuclear explosion. PMID:24304329

Koeman, Elizabeth C; Simonetti, Antonio; Chen, Wei; Burns, Peter C

2013-12-17

83

Composite Materials for Hazard Mitigation of Reactive Metal Hydrides.  

SciTech Connect

In an attempt to mitigate the hazards associated with storing large quantities of reactive metal hydrides, polymer composite materials were synthesized and tested under simulated usage and accident conditions. The composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride. Composites with vinyl-containing siloxane oligomers were also polymerized with and without added styrene and divinyl benzene. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride reduced the inherent hydrogen storage capacity of the material. The composites were found to be initially effective at reducing the amount of heat released during oxidation. However, upon cycling the composites, the mitigating behavior was lost. While the polymer composites we investigated have mitigating potential and are physically robust, they undergo a chemical change upon cycling that makes them subsequently ineffective at mitigating heat release upon oxidation of the metal hydride. Acknowledgements The authors would like to thank the following people who participated in this project: Ned Stetson (U.S. Department of Energy) for sponsorship and support of the project. Ken Stewart (Sandia) for building the flow-through calorimeter and cycling test stations. Isidro Ruvalcaba, Jr. (Sandia) for qualitative experiments on the interaction of sodium alanate with water. Terry Johnson (Sandia) for sharing his expertise and knowledge of metal hydrides, and sodium alanate in particular. Marcina Moreno (Sandia) for programmatic assistance. John Khalil (United Technologies Research Corp) for insight into the hazards of reactive metal hydrides and real-world accident scenario experiments. Summary In an attempt to mitigate and/or manage hazards associated with storing bulk quantities of reactive metal hydrides, polymer composite materials (a mixture of a mitigating polymer and a metal hydride) were synthesized and tested under simulated usage and accident conditions. Mitigating the hazards associated with reactive metal hydrides during an accident while finding a way to keep the original capability of the active material intact during normal use has been the focus of this work. These composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride, in this case a prepared sodium alanate (chosen as a representative reactive metal hydride). It was found that the polymerization of styrene and divinyl benzene could be initiated using AIBN in toluene at 70 degC. The resulting composite materials can be either hard or brittle solids depending on the cross-linking density. Thermal decomposition of these styrene-based composite materials is lower than neat polystyrene indicating that the chemical nature of the polymer is affected by the formation of the composite. The char-forming nature of cross-linked polystyrene is low and therefore, not an ideal polymer for hazard mitigation. To obtain composite materials containing a polymer with higher char-forming potential, siloxane-based monomers were investigated. Four vinyl-containing siloxane oligomers were polymerized with and without added styrene and divinyl benzene. Like the styrene materials, these composite materials exhibited thermal decomposition behavior significantly different than the neat polymers. Specifically, the thermal decomposition temperature was shifted approximately 100 degC lower than the neat polymer signifying a major chemical change to the polymer network. Thermal analysis of the cycled samples was performed on the siloxane-based composite materials. It was found that after 30 cycles the siloxane-containing polymer composite material has similar TGA/DSC-MS traces as the virgin composite material indicating that the polymer is physically intact upon cycling. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride in the form of a composite material reduced the inherent hydrogen storage capacity of the material. This

Pratt, Joseph William; Cordaro, Joseph Gabriel; Sartor, George B.; Dedrick, Daniel E.; Reeder, Craig L.

2012-02-01

84

ENG 4793: Composite Materials and Processes 1 Compression Molding  

E-print Network

1 ENG 4793: Composite Materials and Processes 1 Compression Molding ver 2 ENG 4793: Composite and Processes 4 Schematic of a Compression Molding Press ENG 4793: Composite Materials and Processes 5 Matched Die Mold ENG 4793: Composite Materials and Processes 6 #12;2 ENG 4793: Composite Materials

Colton, Jonathan S.

85

Energy absorption of composite material and structure  

NASA Technical Reports Server (NTRS)

Results are presented from a joint research program on helicopter crashworthiness conducted by the U.S. Army Aerostructures Directorate and NASA Langley. Through the ongoing research program an in-depth understanding has been developed on the cause/effect relationships between material and architectural variables and the energy-absorption capability of composite material and structure. Composite materials were found to be efficient energy absorbers. Graphite/epoxy subfloor structures were more efficient energy absorbers than comparable structures fabricated from Kevlar or aluminum. An accurate method of predicting the energy-absorption capability of beams was developed.

Farley, Gary L.

1987-01-01

86

Natural radioactivity of building materials  

Microsoft Academic Search

Experiments were designed to measure trace uranium concentration and the rate of radon exhalation from masonry structural materials, both bare and surface finished and coated. LR115 cellulose nitrate track detectors were used to record the alpha emission from structural material surface. Fission track, neutron activation and fluorometric analysis methods were used to determine the uranium content. Most types of paints

E. Tamez; M. T. Olguín; N. Segovia; S. Bulbulian; F. Abascal

1986-01-01

87

Cell attachment to hydrogel-electrospun fiber mat composite materials.  

PubMed

Hydrogels, electrospun fiber mats (EFMs), and their composites have been extensively studied for tissue engineering because of their physical and chemical similarity to native biological systems. However, while chemically similar, hydrogels and electrospun fiber mats display very different topographical features. Here, we examine the influence of surface topography and composition of hydrogels, EFMs, and hydrogel-EFM composites on cell behavior. Materials studied were composed of synthetic poly(ethylene glycol) (PEG) and poly(ethylene glycol)-poly(?-caprolactone) (PEGPCL) hydrogels and electrospun poly(caprolactone) (PCL) and core/shell PCL/PEGPCL constituent materials. The number of adherent cells and cell circularity were most strongly influenced by the fibrous nature of materials (e.g., topography), whereas cell spreading was more strongly influenced by material composition (e.g., chemistry). These results suggest that cell attachment and proliferation to hydrogel-EFM composites can be tuned by varying these properties to provide important insights for the future design of such composite materials. PMID:24955629

Han, Ning; Johnson, Jed K; Bradley, Patrick A; Parikh, Kunal S; Lannutti, John J; Winter, Jessica O

2012-01-01

88

Pressure variation assisted fiber extraction and development of high performance natural fiber composites and nanocomposites  

Microsoft Academic Search

It is believed, that due to the large surface areas provided by the nano scale materials, various composite properties could be enhanced when such particles are incorporated into a polymer matrix. There is also a trend of utilizing natural resources or reusing and recycling materials that are already available for the fabrication of the new composite materials. Cellulose is the

Gediminas Markevicius

2010-01-01

89

ISOTOPIC COMPOSITIONS OF URANIUM REFERENCE MATERIALS  

SciTech Connect

Uranium isotopic compositions of a variety of U standard materials were measured at Lawrence Livermore National Laboratory and are reported here. Both thermal ionization mass spectrometry (TIMS) and multi-collector inductively couple plasma mass spectrometry (MC-ICPMS) were used to determine ratios of the naturally occurring isotopes of U. Establishing an internally coherent set of isotopic values for a range of U standards is essential for inter-laboratory comparison of small differences in {sup 238}U/{sup 235}U, as well as the minor isotopes of U. Differences of {approx} 1.3{per_thousand} are now being observed in {sup 238}U/{sup 235}U in natural samples, and may play an important role in understanding U geochemistry where tracing the origin of U is aided by U isotopic compositions. The {sup 238}U/{sup 235}U ratios were measured with a TRITON TIMS using a mixed {sup 233}U-{sup 236}U isotopic tracer to correct for instrument fractionation. this tracer was extremely pure and resulted in only very minor corrections on the measured {sup 238}U/{sup 235}U ratios of {approx} 0.03. The values obtained for {sup 238}U/{sup 235}U are: IRMM184 = 137.698 {+-} 0.020 (n = 15), SRM950a = 137.870 {+-} 0.018 (n = 8), and CRM112a = 137.866 {+-} 0.030 (n = 16). Uncertainties represent 2 s.d. of the population. The measured value for IRMM184 is in near-perfect agreement with the certified value of 137.697 {+-} 0.042. However, the U isotopic compositions of SRM950a and CRM112a are not certified. Minor isotopes of U were determined with a Nu Plasma HR MC-ICPMS and mass bias was corrected by sample/standard bracketing to IRMM184, using its certified {sup 238}U/{sup 235}U ratio. Thus, the isotopic compositions determined using both instruments are compatible. The values obtained for {sup 234}U/{sup 235}U are: SRM950a = (7.437 {+-} 0.043) x 10{sup -3} (n = 18), and CRM112a = (7.281 {+-} 0.050) x 10{sup -3} (n = 16), both of which are in good agreement with published values. The value for {sup 236}U/{sup 235}U in SRM950a was determined to be (8.48 {+-} 2.63) x 10{sup -6}, whereas {sup 236}U was not detected in CRM112a. They are currently obtaining the U isotopic composition of CRM129a. Preliminary results suggest that the {sup 238}U/{sup 235}U ratio is within error, but slightly lower than the certified value of 137.71.

Jacobsen, B; Borg, L; Williams, R; Brennecka, G; Hutcheon, I

2009-09-03

90

Ceramic Aerogel Composite Materials and Characterization  

NASA Technical Reports Server (NTRS)

Aerogels a.k.a "Solid Smoke" are gels with the liquid phase replaced by gas, leaving behind a highly porous material with a nanoscale framework. Due to the porous, nanoscale structure, aerogels have the lowest known density and conductivity of solids. Aerogels have the potential for being a breakthrough material because of their extremely light weight and unique properties. In this paper, we address overcoming their most profound weaknesses: mechanical fragility and very high surface activity, which leads to a lowered sintering temperature. A matrix of ceramic aerogel composite materials was produced to investigate their properties and functionality. Mechanical property measurements and Scanning Electron Micrographs are used to identify trends and structure of these ceramic composite materials. Thermal cycling was used to identify the sintering points of the materials.

White, Susan; Hrubesh, Lawrence W.; Rasky, Daniel J. (Technical Monitor)

1997-01-01

91

Tensile failure criteria for fiber composite materials  

NASA Technical Reports Server (NTRS)

The analysis provides insight into the failure mechanics of these materials and defines criteria which serve as tools for preliminary design material selection and for material reliability assessment. The model incorporates both dispersed and propagation type failures and includes the influence of material heterogeneity. The important effects of localized matrix damage and post-failure matrix shear stress transfer are included in the treatment. The model is used to evaluate the influence of key parameters on the failure of several commonly used fiber-matrix systems. Analyses of three possible failure modes were developed. These modes are the fiber break propagation mode, the cumulative group fracture mode, and the weakest link mode. Application of the new model to composite material systems has indicated several results which require attention in the development of reliable structural composites. Prominent among these are the size effect and the influence of fiber strength variability.

Rosen, B. W.; Zweben, C. H.

1972-01-01

92

Introduction: Atomistic Nature of Materials  

Microsoft Academic Search

Materials are made of atoms. The atomic hypothesis was put forward by the Greek philosopher Demokritos about 25 centuries ago, but was only proven by quantitative arguments in the 19th and 20th centuries, beginning with the work of John Dalton (1766-1844) and through the development of quantum mechanics, the theory that provided a complete and accurate description of the properties

Efthimios Kaxiras; Sidney Yip

2005-01-01

93

Health monitoring method for composite materials  

DOEpatents

An in-situ method for monitoring the health of a composite component utilizes a condition sensor made of electrically conductive particles dispersed in a polymeric matrix. The sensor is bonded or otherwise formed on the matrix surface of the composite material. Age-related shrinkage of the sensor matrix results in a decrease in the resistivity of the condition sensor. Correlation of measured sensor resistivity with data from aged specimens allows indirect determination of mechanical damage and remaining age of the composite component.

Watkins, Jr., Kenneth S. (Dahlonega, GA); Morris, Shelby J. (Hampton, VA)

2011-04-12

94

Computational modeling of composite material fires.  

SciTech Connect

Composite materials behave differently from conventional fuel sources and have the potential to smolder and burn for extended time periods. As the amount of composite materials on modern aircraft continues to increase, understanding the response of composites in fire environments becomes increasingly important. An effort is ongoing to enhance the capability to simulate composite material response in fires including the decomposition of the composite and the interaction with a fire. To adequately model composite material in a fire, two physical model development tasks are necessary; first, the decomposition model for the composite material and second, the interaction with a fire. A porous media approach for the decomposition model including a time dependent formulation with the effects of heat, mass, species, and momentum transfer of the porous solid and gas phase is being implemented in an engineering code, ARIA. ARIA is a Sandia National Laboratories multiphysics code including a range of capabilities such as incompressible Navier-Stokes equations, energy transport equations, species transport equations, non-Newtonian fluid rheology, linear elastic solid mechanics, and electro-statics. To simulate the fire, FUEGO, also a Sandia National Laboratories code, is coupled to ARIA. FUEGO represents the turbulent, buoyantly driven incompressible flow, heat transfer, mass transfer, and combustion. FUEGO and ARIA are uniquely able to solve this problem because they were designed using a common architecture (SIERRA) that enhances multiphysics coupling and both codes are capable of massively parallel calculations, enhancing performance. The decomposition reaction model is developed from small scale experimental data including thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) in both nitrogen and air for a range of heating rates and from available data in the literature. The response of the composite material subject to a radiant heat flux boundary condition is examined to study the propagation of decomposition fronts of the epoxy and carbon fiber and their dependence on the ambient conditions such as oxygen concentration, surface flow velocity, and radiant heat flux. In addition to the computational effort, small scaled experimental efforts to attain adequate data used to validate model predictions is ongoing. The goal of this paper is to demonstrate the progress of the capability for a typical composite material and emphasize the path forward.

Brown, Alexander L.; Erickson, Kenneth L.; Hubbard, Joshua Allen; Dodd, Amanda B.

2010-10-01

95

Thermal expansion properties of composite materials  

NASA Technical Reports Server (NTRS)

Thermal expansion data for several composite materials, including generic epoxy resins, various graphite, boron, and glass fibers, and unidirectional and woven fabric composites in an epoxy matrix, were compiled. A discussion of the design, material, environmental, and fabrication properties affecting thermal expansion behavior is presented. Test methods and their accuracy are discussed. Analytical approaches to predict laminate coefficients of thermal expansion (CTE) based on lamination theory and micromechanics are also included. A discussion is included of methods of tuning a laminate to obtain a near-zero CTE for space applications.

Johnson, R. R.; Kural, M. H.; Mackey, G. B.

1981-01-01

96

Grafting in cellulose - polystyrene composite materials  

SciTech Connect

In order to evaluate the effect of the grafting of polystyrene on model cellulosic fibers, several composite materials were processed, (1) by simply dispersing microfibrils into a polystyrene matrix, (2) by dispersing the same fibers but modified by phenyl groups, (3) by grafting a functionalized polystyrene on the fibers surface and mixing with the matrix. The characterization of the coupling agent used has been performed by several techniques: FTIR, NMR, DSC and elemental analysis. Evidence of grafting onto the fibers surface was displayed by FTIR measurements and elemental analysis. All the composite materials were characterized by DSC, tensile tests and mechanical spectroscopy.

Trejo O`Reilly, J.A.; Cavaille, J.Y.; Dufresne, A. [CERMAV-CNRS, Grenoble (France)] [and others

1995-12-01

97

Composite material characterization for large space structures.  

NASA Technical Reports Server (NTRS)

A program phase to characterize advanced composite materials for a large reflector support truss on the ATS F & G spacecraft is described. The selection of a Hercules Incorporated, 2002M graphite fiber reinforced epoxy material was based on criteria of spacecraft system requirements and the potential of this material to meet these requirements. The objective of this phase was to develop materials data required for development, design, fabrication, test, and flight of a graphite-fiber, reinforced-plastic spacecraft structure. Testing within a temperature range from -300 F to +200 F covered the generation of data for physical, mechanical, thermophysical, and space environmental properties for the selected material. Additional testing covered adhesive bonded joint materials within the temperature ranges of the spacecraft environment. Descriptions of the spacecraft, reflector support truss, design, requirements, materials, tests, and developed data are presented.

Macneill, C. E.

1972-01-01

98

Ground exposure of composite materials for helicopters  

NASA Technical Reports Server (NTRS)

Residual strength results are presented on four composite material systems that were exposed for three years at locations on the North American Continent. The exposure locations are near the areas where Bell Model 206L Helicopters, that are in a NSA/U.S. Army sponsored flight service program, are flying in daily commercial service. The composite systems are: (1) Kevlar-49 fabric/F-185 epoxy; (2) Kevlar-49 fabric/LRF-277 epoxy; (3) Kevlar-49 fabric/CE-306 epoxy; and (4) T-300 Graphite/E-788 epoxy. All material systems exhibited good strength retention in compression and short beam shear. The Kevlar-49/LRF-277 epoxy retained 88 to 93 percent of the baseline strength while the other material systems exceeded 95 percent of baseline strength. Residual tensile strength of all materials did not show a significant reduction. The available moisture absorption data is also presented.

Baker, D. J.

1984-01-01

99

Ultrasonic plate wave evaluation of natural fiber composite panels  

SciTech Connect

Two key shortcomings of many current ultrasonic nondestructive evaluation (NDE) techniques for wood products are the reliance on empirical correlations and the neglect of valuable waveform information. This study examined the feasibility of using fundamental physical relationships along with advanced signal analysis to nondestructively evaluate elastic material properties in natural fiber-based composite panels. An ultrasonic tone burst system was used to excite and receive antisymmetric plate waves in a variety of fiber-based composite panels. Dispersion curves were constructed exhibiting the variation of antisymmetric phase velocity with frequency. Based on fundamental plate wave propagation theory, flexural and transverse shear rigidity values were obtained from the dispersion curves. Excellent agreement of was obtained between NDE and mechanical testing for most panels. This fundamental research advances the state-of-the-art of wood composite panel NDE by providing a more thorough understanding of plate wave propagation and presenting a technique for direct measurement of elastic material properties.

Tucker, Brian J. (BATTELLE (PACIFIC NW LAB)); Bender, Donald A. (Washington State University); Pollock, David G. (Washington State University); Wolcott, Michael P. (Washington State University); FC Beall

2003-06-01

100

Method of making carbon nanotube composite materials  

DOEpatents

The present invention is a method of making a composite polymeric material by dissolving a vinyl thermoplastic polymer, un-functionalized carbon nanotubes and hydroxylated carbon nanotubes and optionally additives in a solvent to make a solution and removing at least a portion of the solvent after casting onto a substrate to make thin films. The material has enhanced conductivity properties due to the blending of the un-functionalized and hydroxylated carbon nanotubes.

O'Bryan, Gregory; Skinner, Jack L; Vance, Andrew; Yang, Elaine Lai; Zifer, Thomas

2014-05-20

101

Synthesizing Smart Polymeric and Composite Materials  

NASA Astrophysics Data System (ADS)

Smart materials have been widely investigated to explore new functionalities unavailable to traditional materials or to mimic the multifunctionality of biological systems. Synthetic polymers are particularly attractive as they already possess some of the attributes required for smart materials, and there are vast room to further enhance the existing properties or impart new properties by polymer synthesis or composite formulation. In this work, three types of smart polymer and composites have been investigated with important new applications: (1) healable polymer composites for structural application and healable composite conductor for electronic device application; (2) conducting polymer polypyrrole actuator for implantable medical device application; and (3) ferroelectric polymer and ceramic nanoparticles composites for electrocaloric effect based solid state refrigeration application. These application entail highly challenging materials innovation, and my work has led to significant progress in all three areas. For the healable polymer composites, well known intrinsically healable polymer 2MEP4F (a Diels-Alder crosslinked polymer formed from a monomer with four furan groups and another monomer with two maleimide groups) was first chosen as the matrix reinforced with fiber. Glass fibers were successfully functionalized with maleimide functional groups on their surface. Composites from functionalized glass fibers and 2MEP4F healable polymer were made to compare with composites made from commercial carbon fibers and 2MEP4F polymer. Dramatically improved short beam shear strength was obtained from composite of functionalized glass fibers and 2MEP4F polymer. The high cost of 2MEP4F polymer can potentially limit the large-scale application of the developed healable composite, we further developed a new healable polymer with much lower cost. This new polymer was formed through the Diels-Alder crosslinking of poly(furfuryl alcohol) (PFA) and 1,1'-(Methylenedi-4,1-phenylene)bismaleimide (MDPB). It showed the same healing ability as 2MEP4F while all starting materials are cheaper and commercially available. To further improve the mechanical strength of the PFA-MDPB healable polymer, epoxy as a strengthening component was mixed with PFA-MDPB healable polymer. The PFA, MDPB and epoxy composite polymers were further reinforced by carbon fiber as done with 2MEP4F matrix and the final composites were proved to have higher short beam shear strength than 2MEP4F while exhibiting a similar healing efficiency. Healable polymer MDPB (a two maleimide groups monomer) -- FGEEDR (a four furan groups monomer) was also designed and synthesized for transparent healable polymer. The MDPB-FGEEDR healable polymer was composited with silver nanowires (AgNWs) to afford healable transparent composite conductor. Razer blade cuts in the composite conductor could heal upon heating to recover the mechanical strength and electrical conductivity of the composite. The healing could be repeated for multiple times on the same cut location. The healing process was as fast as 3 minutes for conductivity to recover 97% of the original value. For electroactive polymer polypyrrole, the fast volume change upon electrical field change due to electrochemical oxidization or reduction was studied for actuation targeting toward a robotic application. The flexibility of polypyrrole was improved via copolymerization with pyrrole derivatives. Actuator devices are fabricated that more suitable for implantable medical device application than pyrrole homopolymer. The change of dipole re-orientation and thus dielectric constant of ferroelectric polymers and ceramics upon electrical field may be exploited for electrocaloric effect (ECE) and solid state refrigeration. For ferroelectric ceramics, we synthesized a series of Ba1-xSrxTiO3 nanoparticles with diameter ranging from 8-12 nm and characterized their dielectric and ferroelectric properties through hysteresis measurement. It was found that 8 nm BaTiO3 nanocrystals are stable at cubic crystal structure without ferroelectric

Gong, Chaokun

102

Composite materials microstructure for radiation shielding  

NASA Technical Reports Server (NTRS)

Shielding against radiation is a concern for applications on earth, in space, and on extraterrestrial surfaces. On earth EMI is an important factor, while in space and on extraterrestrial surfaces particle (high charge-Z and high energy-E) radiation is a critical issue. Conventional metallic materials currently used for EMI shielding incur large weight penalties. To overcome this weight penalty, ultra-lightweight composite materials utilizing fillers ranging from carbon microballoons to silver coated ceramic microballoons are proposed. The crucial shielding requirement is conductivity of the constituent materials, while the hollow microballoon geometry is utilized to yield low weight. Methods of processing and composition effects are examined and these results are compared to the effectiveness of varying the conductive microballoon material. The resulting ultralightweight materials, developed for EMI shielding, can be tailored through the application of the understanding of the relative effects of variables such as those tested. Initial experimental results reveal that these tailored ultralightweight composite materials are superior to traditional aluminum shielding at only a small fraction of the weight.

Radford, Donald W.; Sadeh, Willy Z.; Cheng, Boyle C.

1992-01-01

103

Introduction: Atomistic Nature of Materials  

NASA Astrophysics Data System (ADS)

Materials are made of atoms. The atomic hypothesis was put forward by the Greek philosopher Demokritos about 25 centuries ago, but was only proven by quantitative arguments in the 19th and 20th centuries, beginning with the work of John Dalton (1766-1844) and through the development of quantum mechanics, the theory that provided a complete and accurate description of the properties of atoms. The very large number of atoms encountered in a typical material (of order ˜1024or more) precludes any meaningful description of its properties based on a complete account of the behavior of each and every atom that comprises it. Special cases, such as perfect crystals, are exceptions where symmetry reduces the number of independent atoms to very few; in such cases, the properties of the solid are indeed describable in terms of the behavior of the few independent atoms and this can be accomplished using quantum mechanical methods. However, this is only an idealized model of actual solids in which perfect order is broken either by thermal disorder or by the presence of defects that play a crucial role in determining the physical properties of the system.

Kaxiras, Efthimios; Yip, Sidney

104

Composite materials for rail transit systems  

NASA Technical Reports Server (NTRS)

The potential is explored for using composite materials in urban mass transit systems. The emphasis was to identify specific advantages of composite materials in order to determine their actual and potential usage for carbody and guideway structure applications. The literature was reviewed, contacts were made with major domestic system operators, designers, and builders, and an analysis was made of potential composite application to railcar construction. Composites were found to be in use throughout the transit industry, usually in secondary or auxiliary applications such as car interior and nonstructural exterior panels. More recently, considerable activity has been initiated in the area of using composites in the load bearing elements of civil engineering structures such as highway bridges. It is believed that new and improved manufacturing refinements in pultrusion and filament winding will permit the production of beam sections which can be used in guideway structures. The inherent corrosion resistance and low maintenance characteristics of composites should result in lowered maintenance costs over a prolonged life of the structure.

Griffin, O. Hayden, Jr.; Guerdal, Zafer; Herakovich, Carl T.

1987-01-01

105

Composite materials for precision space reflector panels  

NASA Astrophysics Data System (ADS)

One of the critical technology needs of large precision reflectors for future astrophysical and optical communications satellites lies in the area of structural materials. Results from a materials research and development program at NASA Langley Research Center to provide materials for these reflector applications are discussed. Advanced materials that meet the reflector panel requirements are identified and thermal, mechanical and durability properties of candidate materials after exposure to simulated space environments are compared. Results from analytical studies to define material properties that control laminate properties and reflector deformation are discussed. A parabolic, graphite-phenolic honeycomb composite panel having a surface accuracy of 70.8 microinches RMS and an areal weight of 1.17 lbm/ft2 was fabricated with T50/ERL1962 facesheets, a PAEI thermoplastic surface film, and Al and SiOx coatings.

Tompkins, Stephen S.; Funk, Joan G.; Bowles, David E.; Towell, Timothy W.; Connell, John W.

1992-09-01

106

Thermoplastic Composite Materials for Aerospace Applications  

NASA Astrophysics Data System (ADS)

Mechanical and thermo-physical properties of composites materials with thermoplastic matrix (PEEK/IM7, TPI/IM7 and PPS/IM7) used for aerospace applications have been analyzed as function of two different process techniques: compression molding and fiber placement process "hot gas assisted."

Casula, G.; Lenzi, F.; Vitiello, C.

2008-08-01

107

Silicon nitride reinforced nickel alloy composite materials  

Microsoft Academic Search

An erosion resistant composite material is described comprising silicon nitride rod reinforced nickel alloy, where the silicon nitride is cold pressed and sintered and substantially nonreactive with the alloy at high temperatures. The silicon nitride can either be polycrystalline or amorphous containing alumina, 15% yttria and about 2% to about 5% silica. Three to 8% alumina is used in the

F. S. Galasso; R. D. Veltri

1985-01-01

108

Interaction of pesticides with natural organic material  

USGS Publications Warehouse

Two examples of the interaction of pesticides with natural organic materials have been investigated. Sodium humate solubilizes DDT in water and humic acid strongly sorbs 2,4,5-T. These two types of interactions are indicative of the types that one would expect when any organic pesticide is applied to a natural soil-water system.

Wershaw, R.L.; Burcar, P.J.; Goldberg, M.C.

1969-01-01

109

Satellite surface material composition from synthetic spectra  

NASA Astrophysics Data System (ADS)

The objective of this research was to determine if measurements from a Sagnac interferometer could provide reliable estimates of satellite material composition. The Sagnac interferometer yields a spatial interferogram that can be sampled by a linear detector array. The interferogram is related to the spectrum of the source through a Fourier transform. Here, spectral reflectivities of nine common satellite materials were used to simulate the spectrum on obtains from an ideal Sagnac interferometer in the beam-train of a ground-based telescope whose mission is to view satellites. The signal-to-noise ratio of the spectrum was varied to simulate the effect of range variation between the sensor and the satellite. The simulated spectra consisted of a linear mixture of spectra from two of the nine materials. Three different architectures were developed and their performances compared. One of the three architectures consisted of nine artificial neural networks (ANN's), one for each material, and a linear estimator that estimated the satellite surface area attributable to each material. This method estimates the material composition by using a classifier to identify the materials contributing to the mixture, then eliminating unlikely contributors to the mixture before performing a constrained linear estimate. It is shown that due to high classification errors, the system using solely a linear estimator provides the estimate with the lowest errors.

Caudill, Eugene L.

1994-12-01

110

Composite materials for precision space reflector panels  

NASA Technical Reports Server (NTRS)

One of the critical technology needs of large precision reflectors for future astrophysical and optical communications satellites lies in the area of structural materials. Results from a materials research and development program at NASA Langley Research Center to provide materials for these reflector applications are discussed. Advanced materials that meet the reflector panel requirements are identified, and thermal, mechanical and durability properties of candidate materials after exposure to simulated space environments are compared. A parabolic, graphite-phenolic honeycomb composite panel having a surface accuracy of 70.8 microinches rms and an areal weight of 1.17 lbm/sq ft was fabricated with T50/ERL1962 facesheets, a PAEI thermoplastic surface film, and Al and SiO(x) coatings.

Tompkins, Stephen S.; Funk, Joan G.; Bowles, David E.; Towell, Timothy W.; Connell, John W.

1992-01-01

111

Damping Experiment of Spinning Composite Plates With Embedded Viscoelastic Material  

NASA Technical Reports Server (NTRS)

One way to increase gas turbine engine blade reliability and durability is to reduce blade vibration. It is well known that vibration can be reduced by adding damping to metal and composite blade-disk systems. As part of a joint research effort of the NASA Lewis Research Center and the University of California, San Diego, the use of integral viscoelastic damping treatment to reduce the vibration of rotating composite fan blades was investigated. The objectives of this experiment were to verify the structural integrity of composite plates with viscoelastic material patches embedded between composite layers while under large steady forces from spinning, and to measure the damping and natural frequency variation with rotational speed.

Mehmed, Oral

1998-01-01

112

Development of a novel regenerated cellulose composite material.  

PubMed

We report for the first time on a new natural composite material achieved by blending cotton and duck feather using an ionic liquid. The addition of duck feather was found to improve the elasticity, strain at break, by 50% when compared to regenerated cellulose alone. This is a significant finding since regenerated cotton using ionic liquids often suffers from poor elasticity. The improved elasticity is likely due to the regenerated duck feather maintaining its helical structure. The new regenerated cellulose composites were characterized using a combination of dynamic mechanical analysis, Fourier transform infrared spectroscopy, thermal gravimetric analysis, contact angle measurements and scanning electron microscopy. PMID:25659713

De Silva, Rasike; Vongsanga, Kylie; Wang, Xungai; Byrne, Nolene

2015-05-01

113

Natural Language Processing with Distributional Compositional Models Jean Maillard  

E-print Network

Natural Language Processing with Distributional Compositional Models Jean Maillard Supervised by: Dr Stephen Clark, Computer Laboratory, University of Cambridge Natural Language Processing language. Tradi- tionally, the field has been divided into two "camps": compositional and distri- butional

114

Compression Testing of Textile Composite Materials  

NASA Technical Reports Server (NTRS)

The applicability of existing test methods, which were developed primarily for laminates made of unidirectional prepreg tape, to textile composites is an area of concern. The issue is whether the values measured for the 2-D and 3-D braided, woven, stitched, and knit materials are accurate representations of the true material response. This report provides a review of efforts to establish a compression test method for textile reinforced composite materials. Experimental data have been gathered from several sources and evaluated to assess the effectiveness of a variety of test methods. The effectiveness of the individual test methods to measure the material's modulus and strength is determined. Data are presented for 2-D triaxial braided, 3-D woven, and stitched graphite/epoxy material. However, the determination of a recommended test method and specimen dimensions is based, primarily, on experimental results obtained by the Boeing Defense and Space Group for 2-D triaxially braided materials. They evaluated seven test methods: NASA Short Block, Modified IITRI, Boeing Open Hole Compression, Zabora Compression, Boeing Compression after Impact, NASA ST-4, and a Sandwich Column Test.

Masters, John E.

1996-01-01

115

ENG 4793: Composite Materials and Processes 1 Injection Molding  

E-print Network

1 ENG 4793: Composite Materials and Processes 1 Injection Molding ver 1 ENG 4793: Composite · Ejection force · Design rules ENG 4793: Composite Materials and Processes 3 Equipment Clamp Mold Hopper screw nozzle clamp mold cavity pellets motor / drive throat #12;2 ENG 4793: Composite Materials

Colton, Jonathan S.

116

ACEE Composite Structures Technology: Review of selected NASA research on composite materials and structures  

NASA Technical Reports Server (NTRS)

The NASA Aircraft Energy Efficiency (ACEE) Composite Primary Aircraft Structures Program was designed to develop technology for advanced composites in commercial aircraft. Research on composite materials, aircraft structures, and aircraft design is presented herein. The following parameters of composite materials were addressed: residual strength, damage tolerance, toughness, tensile strength, impact resistance, buckling, and noise transmission within composite materials structures.

1984-01-01

117

Soaring to New Heights in Natural Materials  

NASA Astrophysics Data System (ADS)

Feathers are the most distinguishable feature of all modern Aves. Flight feathers exemplify several materials science phenomena. The most obvious attribute is the branching or hierarchical structure at macroscale to mesoscale. The primary shaft, or rachis from which secondary features project, of the flight feather is a sandwich structured composite. The thin brittle cortex of the rachis and barbules encloses a relatively thick, low-density medullary core or cellular solid. The cortex of the rachis is constructed as a fiber-reinforcement composite, and structural variations along the length of the feather invoke the comparison to functionally graded materials. We have studied microstructure and mechanical properties of the feather rachis in a piecewise fashion, and we will present results of investigations of the mechanical behavior and failure of the composite and parts thereof in tension, compression, and flexure.

Bodde, Sara; Kiang, James; McKittrick, Joanna

2011-03-01

118

Putting it Together: The Science and Technology of Composite Materials  

NSDL National Science Digital Library

Composite materials are light, strong, corrosion-resistant composites of two or more materials used commonly in manufacturing. This recent report is from the Australian Academy of Science with support from The Cooperative Research Centre for Advanced Composite Structures, Ltd. and the Commonwealth Department of Industry, Science and Resources. It gives information on the history, manufacturing techniques, and efficiency of composite materials. A glossary, reference list, and links to educational sites as well as other composite materials sites are also featured.

2000-01-01

119

Multiaxial analysis of dental composite materials.  

PubMed

Dental composites are subjected to extreme chemical and mechanical conditions in the oral environment, contributing to the degradation and ultimate failure of the material in vivo. The objective of this study is to validate an alternative method of mechanically loading dental composite materials. Confined compression testing more closely represents the complex loading that dental restorations experience in the oral cavity. Dental composites, a nanofilled and a hybrid microfilled, were prepared as cylindrical specimens, light-cured in ring molds of 6061 aluminum, with the ends polished to ensure parallel surfaces. The samples were subjected to confined compression loading to 3, 6, 9, 12, and 15% axial strain. Upon loading, the ring constrains radial expansion of the specimen, generating confinement stresses. A strain gage placed on the outer wall of the aluminum confining ring records hoop strain. Assuming plane stress conditions, the confining stress (sigma(c)) can be calculated at the sample/ring interface. Following mechanical loading, tomographic data was generated using a high-resolution microtomography system developed at beamline 2-BM of the Advanced Photon Source at Argonne National Laboratory. Extraction of the crack and void surfaces present in the material bulk is numerically represented as crack edge/volume (CE/V), and calculated as a fraction of total specimen volume. Initial results indicate that as the strain level increases the CE/V increases. Analysis of the composite specimens under different mechanical loads suggests that microtomography is a useful tool for three-dimensional evaluation of dental composite fracture surfaces. PMID:18506811

Kotche, Miiri; Drummond, James L; Sun, Kang; Vural, Murat; DeCarlo, Francesco

2009-02-01

120

Aromatic acetylenes for carbon matrix composite material  

SciTech Connect

Carbon composite materials are being used increasingly in aerospace structures because of the high strength to weight ratio of such materials. Acetylenic substituted aromatic compounds, which have low melting points, can be easily processed, lose little weight during their curing, and do not need multiple impregnations to achieve high density, are good candidates as carbon precursor materials. In this laboratory, the compound 1,2,4,5-tetrakis(phenylethynyl)benzene 1 was prepared by the palladium catalyzed reaction of phenylacetylene with 1,2,4,5-tetrabromobenzene in the presence of excess amine base. Laboratory studies have shown that 1 melts at 195{degrees}C and forms a thermosetting material with high thermal and oxidative stability and a high char yield upon pyrolysis under nitrogen. Changes which occurred upon pyrolysis in air were studied by infrared spectroscopy. The monomer 1 is a crystalline solid that is stable indefinitely at room temperature.

Jones, K.M.; Keller, T.M. [Naval Research Lab., Washington, DC (United States)

1993-12-31

121

Using Composite Materials in a Cryogenic Pump  

NASA Technical Reports Server (NTRS)

Several modifications have been made to the design and operation of an extended-shaft cryogenic pump to increase the efficiency of pumping. In general, the efficiency of pumping a cryogenic fluid is limited by thermal losses which is itself caused by pump inefficiency and leakage of heat through the pump structure. A typical cryogenic pump includes a drive shaft and two main concentric static components (an outer pressure containment tube and an intermediate static support tube) made from stainless steel. The modifications made include replacement of the stainless-steel drive shaft and the concentric static stainless-steel components with components made of a glass/epoxy composite. The leakage of heat is thus reduced because the thermal conductivity of the composite is an order of magnitude below that of stainless steel. Taking advantage of the margin afforded by the decrease in thermal conductivity, the drive shaft could be shortened to increase its effective stiffness, thereby increasing the rotordynamic critical speeds, thereby further making it possible to operate the pump at a higher speed to increase pumping efficiency. During the modification effort, an analysis revealed that substitution of the shorter glass/epoxy shaft for the longer stainless-steel shaft was not, by itself, sufficient to satisfy the rotordynamic requirements at the desired increased speed. Hence, it became necessary to increase the stiffness of the composite shaft. This stiffening was accomplished by means of a carbon-fiber-composite overwrap along most of the length of the shaft. Concomitantly with the modifications described thus far, it was necessary to provide for joining the composite-material components with metallic components required by different aspects of the pump design. An adhesive material formulated specially to bond the composite and metal components was chosen as a means to satisfy these requirements.

Batton, William D.; Dillard, James E.; Rottmund, Matthew E.; Tupper, Michael L.; Mallick, Kaushik; Francis, William H.

2008-01-01

122

Metal Matrix Composite Materials for Aerospace Applications  

NASA Technical Reports Server (NTRS)

Metal matrix composites (MMC) are attractive materials for aerospace applications because of their high specific strength, high specific stiffness, and lower thermal expansion coefficient. They are affordable since complex parts can be produced by low cost casting process. As a result there are many commercial and Department of Defense applications of MMCs today. This seminar will give an overview of MMCs and their state-of-the-art technology assessment. Topics to be covered are types of MMCs, fabrication methods, product forms, applications, and material selection issues for design and manufacture. Some examples of current and future aerospace applications will also be presented and discussed.

Bhat, Biliyar N.; Jones, C. S. (Technical Monitor)

2001-01-01

123

Advanced Technology Composite Fuselage - Materials and Processes  

NASA Technical Reports Server (NTRS)

The goal of Boeing's Advanced Technology Composite Aircraft Structures (ATCAS) program was to develop the technology required for cost and weight efficient use of composite materials in transport fuselage structure. This contractor report describes results of material and process selection, development, and characterization activities. Carbon fiber reinforced epoxy was chosen for fuselage skins and stiffening elements and for passenger and cargo floor structures. The automated fiber placement (AFP) process was selected for fabrication of monolithic and sandwich skin panels. Circumferential frames and window frames were braided and resin transfer molded (RTM'd). Pultrusion was selected for fabrication of floor beams and constant section stiffening elements. Drape forming was chosen for stringers and other stiffening elements. Significant development efforts were expended on the AFP, braiding, and RTM processes. Sandwich core materials and core edge close-out design concepts were evaluated. Autoclave cure processes were developed for stiffened skin and sandwich structures. The stiffness, strength, notch sensitivity, and bearing/bypass properties of fiber-placed skin materials and braided/RTM'd circumferential frame materials were characterized. The strength and durability of cocured and cobonded joints were evaluated. Impact damage resistance of stiffened skin and sandwich structures typical of fuselage panels was investigated. Fluid penetration and migration mechanisms for sandwich panels were studied.

Scholz, D. B.; Dost, E. F.; Flynn, B. W.; Ilcewicz, L. B.; Nelson, K. M.; Sawicki, A. J.; Walker, T. H.; Lakes, R. S.

1997-01-01

124

Test Plan for Composite Hydrogen Getter Materials  

Microsoft Academic Search

The intent of this test plan is to provide details of the Savannah River Technology Center (SRTC) effort to evaluate composite getter materials for eventual use in expanding the wattage limits for transportation of contact-handled transuranic waste (CH-TRU). This effort is funded by the Mixed Waste Focus Area (MWFA) under Technical Task Plan (TTP) SR-1-9-MW-45 and is the result of

2000-01-01

125

Machine augmented composite materials for damping purposes  

E-print Network

???????........??...27 4. INVESTIGATION OF FLUID FLOW IN AND INTERACTION WITH TUBES EMBEDDED IN A MATRIX............................................................38 4.1 Modeling of Sealed Tubes Embedded in an Elastomer Matrix??....??..38.... On the other hand, common elastomers possess good damping characteristics and low density, but they have relatively low stiffness and strength. Conventional composite materials have large stiffness to density ratios, but many lack good damping properties...

McCutcheon, David Matthew

2005-02-17

126

Silicon nitride reinforced nickel alloy composite materials  

SciTech Connect

An erosion resistant composite material is described comprising silicon nitride rod reinforced nickel alloy, where the silicon nitride is cold pressed and sintered and substantially nonreactive with the alloy at high temperatures. The silicon nitride can either be polycrystalline or amorphous containing alumina, 15% yttria and about 2% to about 5% silica. Three to 8% alumina is used in the case of polycrystalline silicon nitride and 2% to 6% alumina is used in the case of amorphous silicon nitride.

Galasso, F. S.; Veltri, R. D.

1985-10-29

127

Mechanics Methodology for Textile Preform Composite Materials  

NASA Technical Reports Server (NTRS)

NASA and its contractors have completed a program to develop a basic mechanics underpinning for textile composites. Three major deliverables were produced by the program: 1. A set of test methods for measuring material properties and design allowables; 2. Mechanics models to predict the effects of the fiber preform architecture and constituent properties on engineering moduli, strength, damage resistance, and fatigue life; and 3. An electronic data base of coupon type test data. This report describes these three deliverables.

Poe, Clarence C., Jr.

1996-01-01

128

Impact of solids on composite materials  

NASA Technical Reports Server (NTRS)

The failure modes of composite materials as a result of low velocity impact were investigated by simulating the impact with a finite element analysis. An important facet of the project is the modeling of the impact of a solid onto cylindrical shells composed of composite materials. The model under development will simulate the delamination sustained when a composite material encounters impact from another rigid body. The computer equipment was installed, the computer network tested, and a finite element method model was developed to compare results with known experimental data. The model simulated the impact of a steel rod onto a rotating shaft. Pre-processing programs (GMESH and TANVEL) were developed to generate node and element data for the input into the three dimensional, dynamic finite element analysis code (DYNA3D). The finite element mesh was configured with a fine mesh near the impact zone and a coarser mesh for the impacting rod and the regions surrounding the impacting zone. For the computer simulation, five impacting loads were used to determine the time history of the stresses, the scribed surface areas, and the amount of ridging. The processing time of the computer codes amounted from 1 to 4 days. The calculated surface area were within 6-12 percent, relative error when compated to the actual scratch area.

Bronson, Arturo; Maldonado, Jerry; Chern, Tzong; Martinez, Francisco; Mccord-Medrano, Johnnie; Roschke, Paul N.

1987-01-01

129

Mimicry of natural material designs and processes  

NASA Astrophysics Data System (ADS)

Biological structural materials, although composed of unremarkable substances synthesized at low temperatures, often exhibit superior mechanical properties. In particular, the quality in which nearly all biologically derived materials excel is toughness. The advantageous mechanical properties are attributable to the hierarchical, composite, structural arrangements common to biological systems. Materials scientists and engineers have increasingly recognized that biological designs or processing approaches applied to man-made materials (biomimesis) may offer improvements in performance over conventional designs and fabrication methods. In this survey, the structures and processing routes of marine shells, avian eggshells, wood, bone, and insect cuticle are briefly reviewed, and biomimesis research inspired by these materials is discussed. In addition, this paper describes and summarizes the applications of biomineralization, self-assembly, and templating with proteins to the fabrication of thin ceramic films and nanostructure devices.

Bond, G. M.; Richman, R. H.; McNaughton, W. P.

1995-06-01

130

Composite material systems for hydrogen management  

NASA Technical Reports Server (NTRS)

The task of managing hydrogen entry into elevated temperature structural materials employed in turbomachinery is a critical engineering area for propulsion systems employing hydrogen or decomposable hydrocarbons as fuel. Extant structural materials, such as the Inconel series, are embrittled by the ingress of hydrogen in service, leading to a loss of endurance and general deterioration of load-bearing dependability. Although the development of hydrogen-insensitive material systems is an obvious engineering option, to date insensitive systems cannot meet the time-temperature-loading service extremes encountered. A short-term approach that is both feasible and technologically sound is the development and employment of hydrogen barrier coatings. The present project is concerned with developing, analyzing, and physically testing laminate composite hydrogen barrier systems, employing Inconel 718 as the structural material to be protected. Barrier systems will include all metallic, metallic-to-ceramic, and, eventually, metallic/ceramic composites as the lamellae. Since space propulsion implies repetitive engine firings without earth-based inspection and repair, coating durability will be closely examined, and testing regimes will include repetitive thermal cycling to simulate damage accumulation. The target accomplishments include: generation of actual hydrogen permeation data for metallic, ceramic-metallic, and hybrid metallic/ceramic composition barrier systems, practically none of which is currently extant; definition of physical damage modes imported to barrier systems due to thermal cycling, both transient temperature profiles and steady-state thermal mismatch stress states being examined as sources of damage; and computational models that incorporate general laminate schemes as described above, including manufacturing realities such as porosity, and whatever defects are introduced through service and characterized during the experimental programs.

Pangborn, R. N.; Queeney, R. A.

1991-01-01

131

Polymer-composite materials for radiation protection.  

PubMed

Unwanted exposures to high-energy or ionizing radiation can be hazardous to health. Prolonged or accumulated radiation dosage from either particle-emissions such as alpha/beta, proton, electron, neutron emissions, or high-energy electromagnetic waves such as X-rays/? rays, may result in carcinogenesis, cell mutations, organ failure, etc. To avoid occupational hazards from these kinds of exposures, researchers have traditionally used heavy metals or their composites to attenuate the radiation. However, protective gear made of heavy metals are not only cumbersome but also are capable of producing more penetrative secondary radiations which requires additional shielding, increasing the cost and the weight factor. Consequently, significant research efforts have been focused toward designing efficient, lightweight, cost-effective, and flexible shielding materials for protection against radiation encountered in various industries (aerospace, hospitals, and nuclear reactors). In this regard, polymer composites have become attractive candidates for developing materials that can be designed to effectively attenuate photon or particle radiation. In this paper, we review the state-of-the-art of polymer composites reinforced with micro/nanomaterials, for their use as radiation shields. PMID:23009182

Nambiar, Shruti; Yeow, John T W

2012-11-01

132

TREATMENT OF STORMWATER BY NATURAL ORGANIC MATERIALS  

EPA Science Inventory

The overall objective of this study was to evaluate the feasibility of using low-cost natural filter materials for stormwater (SW) treatment. Generic mulch, pine bark mulch, and processed jute were evaluated for metal and organic pollutant removal from actual SW samples collected...

133

Active composite materials as sensing elements for fiber-reinforced smart composite structures  

Microsoft Academic Search

Polymer based piezoelectric composite materials can be readily integrated within laminated composite structures to provide sensing and actuating capabilities. In this study composite films of ferroelectric ceramic\\/polymer materials have been developed and characterized as in-situ multi purpose sensing elements for the nondestructive monitoring of fiber reinforced composites. In this paper the response of embedded composite films to simulated acoustic emission

Panagiotis Blanas; Matthew P. Wenger; Elias J. Rigas; Dilip K. Das-Gupta

1998-01-01

134

Glasses, ceramics, and composites from lunar materials  

NASA Technical Reports Server (NTRS)

A variety of useful silicate materials can be synthesized from lunar rocks and soils. The simplest to manufacture are glasses and glass-ceramics. Glass fibers can be drawn from a variety of basaltic glasses. Glass articles formed from titania-rich basalts are capable of fine-grained internal crystallization, with resulting strength and abrasion resistance allowing their wide application in construction. Specialty glass-ceramics and fiber-reinforced composites would rely on chemical separation of magnesium silicates and aluminosilicates as well as oxides titania and alumina. Polycrystalline enstatite with induced lamellar twinning has high fracture toughness, while cordierite glass-ceramics combine excellent thermal shock resistance with high flexural strengths. If sapphire or rutile whiskers can be made, composites of even better mechanical properties are envisioned.

Beall, George H.

1992-01-01

135

Recycling technologies for thermoset composite materials—current status  

Microsoft Academic Search

The technologies for recycling thermoset composite materials are reviewed. Mechanical recycling techniques involve the use of grinding techniques to comminute the scrap material and produce recyclate products in different size ranges suitable for reuse as fillers or partial reinforcement in new composite material. Thermal recycling processes involve the use of heat to break the scrap composite down and a range

S. J. Pickering

2006-01-01

136

Composite materials flown on the Long Duration Exposure Facility  

NASA Technical Reports Server (NTRS)

Organic composite test specimens were flown on several LDEF experiments. Both bare and coated composites were flown. Atomic oxygen eroded bare composite material, with the resins being recessed at a greater rate than the fibers. Selected coating techniques protected the composite substrate in each case. Tensile and optical properties are reported for numerous specimens. Fiberglass and metal matrix composites were also flown.

George, Pete E.; Dursch, Harry W.; Pippin, H. Gary

1995-01-01

137

Degradation study of date palm fibre\\/polypropylene composites in natural and artificial weathering: mechanical and thermal analysis  

Microsoft Academic Search

Date palm leaves were compounded with polypropylene (PP) and UV stabilizers to form composite materials. The stability of the composites in natural weathering conditions of Saudi Arabia and in accelerated weathering conditions was investigated. The composites were found to be much more stable than PP under the severe natural weathering conditions of Saudi Arabia and in accelerated weathering trials. Compatibilized

B. F Abu-Sharkh; H Hamid

2004-01-01

138

Composite and diamond cold cathode materials  

SciTech Connect

Cold-cathode technology for Crossed-Field Amplifiers (CFAs) has not changed significantly over the last thirty years. The material typically used for cold cathode CFAs is either platinum (Pt) or beryllium (Be), although numerous other materials with higher secondary electron emission ratios have been tested. Beryllium cathodes display higher secondary emission ratios, {approximately} 3.4, than Pt, but require a partial pressure of oxygen to maintain a beryllium oxide (BeO) surface layer. These dispensers limit the life of the CFA, both directly, due to oxygen-source filament burnout, and indirectly, by the production of undesirable gases which adversely affect the performance of the CFA. In an attempt to reduce or eliminate the required oxygen dispenser output level, cathodes were constructed from three varieties of Be/BeO composite material and tested in L-4808s, standard forward-wave AEGIS CFAs. Diamond and diamond-like carbons are desirable as cathode materials because of their extremely high secondary electron emission ratio, greater than 20, but their use has previously been prohibitive because of cost, available, and physical characteristics. Because of recent advances in diamond growth technology it is now possible to deposit thin layers of diamond on a variety of geometric objects. In coordination with Penn State University four annular diamond emitters have been fabricated. The diamond emitters will be tested in a standard AEGIS CFA, both under vacuum and with a partial pressure of hydrogen.

Worthington, M.S.; Wheeland, C.L.; Ramacher, K.; Doyle, E. [Litton Systems Inc., Williamsport, PA (United States). Electron Devices Div.

1996-12-31

139

The spectroscopic study of building composites containing natural sorbents  

NASA Astrophysics Data System (ADS)

This work presents the results of FT-IR spectroscopic studies of heavy metal cations (Ag +, Pb 2+, Zn 2+, Cd 2+ and Cr 3+) immobilization from aqueous solutions on natural sorbents. The sorption has been conducted on sodium forms of zeolite (clinoptilolite) and clay minerals (mixtures containing mainly montmorillonite and kaolinite) which have been separated from natural Polish deposit. In the next part of the work both sorbents were used to obtain new building composites. It was proven those heavy metal cations' sorption causes changes in IR spectra of the zeolite and clay minerals. These alterations are dependent on the way the cations were sorbed. In the case of zeolite, variations of the bands corresponding to the characteristic ring vibrations have been observed. These rings occur in pseudomolecular complexes 4-4-1 (built of alumino- and silicooxygen tetrahedra) which constitute the secondary building units (SBU) and form spatial framework of the zeolite. The most significant changes have been determined in the region of pseudolattice vibrations (650-700 cm -1). In the instance of clay minerals, changes in the spectra occur at two ranges: 1200-800 cm -1 - the range of the bands assigned to asymmetric Si-O(Si,Al) and bending Al-OH vibrations and 3800-3000 cm -1 - the range of the bands originating from OH - groups stretching vibrations. Next results indicate possibilities of applying the used natural sorbents for the obtainment of new building materials having favourable composition and valuable properties. The zeolite was used for obtaining autoclaved materials with an addition of CaO, and the clay minerals for ceramic sintered materials with an addition of quartz and clinoptilolite were produced. FT-IR studies were also conducted on the obtained materials.

Król, M.; Mozgawa, W.

2011-08-01

140

The spectroscopic study of building composites containing natural sorbents.  

PubMed

This work presents the results of FT-IR spectroscopic studies of heavy metal cations (Ag(+), Pb(2+), Zn(2+), Cd(2+) and Cr(3+)) immobilization from aqueous solutions on natural sorbents. The sorption has been conducted on sodium forms of zeolite (clinoptilolite) and clay minerals (mixtures containing mainly montmorillonite and kaolinite) which have been separated from natural Polish deposit. In the next part of the work both sorbents were used to obtain new building composites. It was proven those heavy metal cations' sorption causes changes in IR spectra of the zeolite and clay minerals. These alterations are dependent on the way the cations were sorbed. In the case of zeolite, variations of the bands corresponding to the characteristic ring vibrations have been observed. These rings occur in pseudomolecular complexes 4-4-1 (built of alumino- and silicooxygen tetrahedra) which constitute the secondary building units (SBU) and form spatial framework of the zeolite. The most significant changes have been determined in the region of pseudolattice vibrations (650-700 cm(-1)). In the instance of clay minerals, changes in the spectra occur at two ranges: 1200-800 cm(-1)--the range of the bands assigned to asymmetric Si-O(Si,Al) and bending Al-OH vibrations and 3800-3000 cm(-1)--the range of the bands originating from OH(-) groups stretching vibrations. Next results indicate possibilities of applying the used natural sorbents for the obtainment of new building materials having favourable composition and valuable properties. The zeolite was used for obtaining autoclaved materials with an addition of CaO, and the clay minerals for ceramic sintered materials with an addition of quartz and clinoptilolite were produced. FT-IR studies were also conducted on the obtained materials. PMID:20869299

Król, M; Mozgawa, W

2011-08-15

141

Single-walled carbon nanotube networks in conductive composite materials.  

PubMed

Electrically conductive composite materials can be used for a wide range of applications because they combine the advantages of a specific polymeric material (e.g., thermal and mechanical properties) with the electrical properties of conductive filler particles. However, the overall electrical behaviour of these composite materials is usually much below the potential of the conductive fillers, mainly because by mixing two different components, new interfaces and interphases are created, changing the properties and behaviours of both. Our goal is to characterize and understand the nature and influence of these interfaces on the electrical properties of composite materials. We have improved a technique based on the use of sodium carboxymethyl cellulose (CMC) to disperse single-walled carbon nanotubes (SWCNTs) in water, followed by coating glass substrates, and drying and removing the CMC with a nitric acid treatment. We used electron microscopy and atomic force microscopy techniques to characterize the SWCNT films, and developed an in situ resistance measurement technique to analyse the influence of both the individual components and the mixture of an epoxy/amine system on the electrical behaviour of the SWCNTs. The results showed that impregnating a SWCNT network with a polymer is not the only factor that affects the film resistance; air exposure, temperature, physical and chemical properties of the individual polymer components, and also the formation of a polymeric network, can all have an influence on the macroscopic electrical properties of the initial SWCNT network. These results emphasize the importance of understanding the effects that each of the components can have on each other before trying to prepare an efficient polymer composite material. PMID:25430670

Bârsan, Oana A; Hoffmann, Günter G; van der Ven, Leo G J; de With, G Bert

2014-01-01

142

Synthesis of High Performance Thermoelectric Materials Directly from Natural Mineral  

NASA Astrophysics Data System (ADS)

We report high performance TE materials synthesized directly from natural mineral. Lattice dynamics and electronic band structure calculations suggest that the compound tetrahedrite (Cu12-xMxSb4S13), where M is transition metal such as Zn or Fe, will have low lattice thermal conductivity and good electronic transport properties. We have experimentally investigated the relationship between ZT and x content of different transition metals in synthetic tetrahedrites. We have found that the maximum of ZT value is not sensitive to the value of x but is related to valence band hole filling fraction; high ZT can be maintained over a large range of x. The compositions studied span the range of those of natural mineral tetrahedrite. To demonstrate that the natural mineral itself can be used as a source material, we synthesized samples by mixing natural mineral with synthetic Cu12Sb4S13 by balling milling and hot pressing. The resulting samples were single phase with hole filling fraction in the optimum range and displayed maximum ZT values of unity at 723K. This new synthesis method can directly use natural mineral to produce TE materials in large quantities with little effort.

Lu, Xu; Morelli, Donald; Xia, Yi; Zhou, Fei; Ozolins, Vidvuds; Chi, Hang; Zhou, Xiaoyuan; Uher, Ctirad

2013-03-01

143

Reuse of Material Containing Natural Radionuclides - 12444  

SciTech Connect

Disposal of and use of wastes containing natural radioactive material (NORM) or technologically enhanced natural radioactive material (TENORM) with excessive natural background as a building material is very important in the supervision body activity. At the present time, the residents of Octyabrsky village are under resettlement. This village is located just near the Priargunsky mining and chemical combine (Ltd. 'PPGHO'), one of the oldest uranium mines in our country. The vacated wooden houses in the village are demolished and partly used as a building material. To address the issue of potential radiation hazard of the wooden beams originating from demolition of houses in Octyabrsky village, the contents of the natural radionuclides (K-40, Th-232, Ra-226, U- 238) are being determined in samples of the wooden beams of houses. The NORM contents in the wooden house samples are higher, on average, than their content in the reference sample of the fresh wood shavings, but the range of values is rather large. According to the classification of waste containing the natural radionuclides, its evaluation is based on the effective specific activity. At the effective specific activity lower 1.5 kBq/kg and gamma dose rate lower 70 ?R/h, the material is not considered as waste and can be used in building by 1 - 3 classes depending upon A{sub eff} value. At 1.5 kBq/kg < A{sub eff} ? 4 kBq/kg (4 class), the wooden beams might be used for the purpose of the industrial building, if sum of ratios between the radionuclide specific activity and its specific activity of minimum significance is lower than unit. The material classified as the waste containing the natural radionuclides has A{sub eff} higher 1.5 kBq /kg, and its usage for the purpose of house-building and road construction is forbidden. As for the ash classification and its future usage, such usage is unreasonable, because, according to the provided material, more than 50% of ash samples are considered as radioactive waste containing natural radionuclides. All materials originated from demolition of houses in Octyabrsky village are subjected to the obligatory radiation control. The decision to use the wooden beams shall enter into force after agreement with the State Sanitary and Epidemiological Supervision bodies. Conclusions: 1 - The wooden beam originated from the house demolition in Octyabrsky village might be used as the construction material only in case of compliance with the requirements of the regulatory documents, as well as under approval of the authorities responsible for the state sanitary and epidemiological supervision in this area. 2 - The industrial control is introduced to verify the compliance with the current regulations. 3 - The material originated from the house demolition might be used only if such usage does not cause increasing radiation exposure to the public. (authors)

Metlyaev, E.G.; Novikova, N.J. [Burnasyan Federal Medical Biophysical Centre, Moscow (Russian Federation)

2012-07-01

144

New topics on nanoindentation of polymers and composite materials  

NASA Astrophysics Data System (ADS)

In this study, nanoindentation was used to determine Young's modulus of homogeneous plastic materials as well as inhomogeneous epoxy woven fabric composites using various indenters. In the first part, homogeneous PMMA and polycarbonate were characterized using conical and spherical indenters. The conventional approach of the inverse analysis was modified in order to account for effects obtained during spherical nanoindentation. The experimental results were verified using FEA analysis in ABAQUS. It was found that viscous effects were present in conical nanoindentations which led to an overestimation of contact stiffness. The second part, the response of carbon and glass fiber woven fabric epoxy composites was investigated using Berkovich and spherical indenters. Localized nanoindentation was performed using the Berkovich probe in both materials which led to determination of glass fibers and matrix stiffnesses. The anisotropic nature of the response was treated modifying the classical approach to calculate transverse modulus of a unidirectional composite. Finally, fiber volume ratios were calculated according to type of composite and indenter used.

Martinez Hernandez, Ricardo

145

Wetting, superhydrophobicity, and icephobicity in biomimetic composite materials  

NASA Astrophysics Data System (ADS)

Recent developments in nano- and bio-technology require new materials. Among these new classes of materials which have emerged in the recent years are biomimetic materials, which mimic structure and properties of materials found in living nature. There are a large number of biological objects including bacteria, animals and plants with properties of interest for engineers. Among these properties is the ability of the lotus leaf and other natural materials to repel water, which has inspired researchers to prepare similar surfaces. The Lotus effect involving roughness-induced superhydrophobicity is a way to design nonwetting, self-cleaning, omniphobic, icephobic, and antifouling surfaces. The range of actual and potential applications of superhydrophobic surfaces is diverse including optical, building and architecture, textiles, solar panels, lab-on-a-chip, microfluidic devices, and applications requiring antifouling from biological and organic contaminants. In this thesis, in chapter one, we introduce the general concepts and definitions regarding the wetting properties of the surfaces. In chapter two, we develop novel models and conduct experiments on wetting of composite materials. To design sustainable superhydrophobic metal matrix composite (MMC) surfaces, we suggest using hydrophobic reinforcement in the bulk of the material, rather than only at its surface. We experimentally study the wetting properties of graphite-reinforced Al- and Cu-based composites and conclude that the Cu-based MMCs have the potential to be used in the future for the applications where the wear-resistant superhydrophobicity is required. In chapter three, we introduce hydrophobic coating at the surface of concrete materials making them waterproof to prevent material failure, because concretes and ceramics cannot stop water from seeping through them and forming cracks. We create water-repellant concretes with CA close to 160o using superhydrophobic coating. In chapter four, experimental data are collected in terms of oleophobicity especially when underwater applications are of interest. We develop models for four-phase rough interface of underwater oleophobicity and develop a novel approach to predict the CA of organic liquid on the rough surfaces immersed in water. We investigate wetting transition on a patterned surface in underwater systems, using a phase field model. We demonstrated that roughening on an immersed solid surface can drive the transition from Wenzel to Cassie-Baxter state. This discovery improves our understanding of underwater systems and their surface interactions during the wetting phenomenon and can be applied for the development of underwater oil-repellent materials which are of interest for various applications in the water industry, and marine devices. In chapter five, we experimentally and theoretically investigate the icephobicity of composite materials. A novel comprehensive definition of icephobicity, broad enough to cover a variety of situations including low adhesion strength, delayed ice crystallization, and bouncing is determined. Wetting behavior and ice adhesion properties of various samples are theoretically and experimentally compared. We conclude superhydrophobic surfaces are not necessarily icephobic. The models are tested against the experimental data to verify the good agreement between them. The models can be used for the design of novel superhydrophobic, oleophobic, omniphobic and icephobic composite materials. Finally we conclude that creating surface micro/nanostructures using mechanical abrasion or chemical etching as well as applying low energy materials are the most simple, inexpensive, and durable techniques to create superhydrophobic, oleophobic, and icephobic materials.

Hejazi, Vahid

146

Questa Baseline and Pre-Mining Ground-Water Quality Investigation. 19. Leaching Characteristics of Composited Materials from Mine Waste-Rock Piles and Naturally Altered Areas near Questa, New Mexico  

USGS Publications Warehouse

The goal of this study is to compare and contrast the leachability of metals and the acidity from individual mine waste-rock piles and natural erosional scars in the study area near Questa, New Mexico. Surficial multi-increment (composite) samples less than 2 millimeters in diameter from five waste-rock piles, nine erosional-scar areas, a less-altered site, and a tailings slurry-pipe sample were analyzed for bulk chemistry and mineralogy and subjected to two back-to-back leaching procedures. The first leaching procedure, the U.S. Geological Survey Field Leach Test (FLT), is a short-duration leach (5-minute shaking and 10-minute settling) and is intended to leach readily soluble materials. The FLT was immediately followed by an 18-hour, end-over-end rotation leaching procedure. Comparison of results from the back-to-back leaching procedures can provide information about reactions that may take place upon migration of leachates through changing geochemical conditions (for example, pH changes), both within the waste-rock and scar materials and away from the source materials. For the scar leachates, the concentrations of leachable metals varied substantially between the scar areas sampled. The scar leachates have low pH (pH 3.2-4.1). Under these low-pH conditions, cationic metals are solubilized and mobile, but anionic species, such as molybdenum, are less soluble and less mobile. Generally, metal concentrations in the waste-rock leachates did not exceed the upper range of those metal concentrations in the erosional-scar leachates. One exception is molybdenum, which is notably higher in the waste-rock leachates compared with the scar leachates. Most of the waste-rock leachates were at least mildly acidic (pH 3.0-6.2). The pH values in the waste-rock leachates span a large pH range that includes some pH-dependent solubility and metal-attenuation reactions. An increase in pH with leaching time and agitation indicates that there is pH-buffering capacity in some of the waste-rock piles. As pH increased in the waste-pile leachates, concentrations of several metals decreased with increasing time and agitation. Similar pH-dependent reactions may take place upon migration of the leachates in the waste-rock piles. Bulk chemistry, mineralogy, and leachate sulfur-isotope data indicate that the Capulin and Sugar Shack West waste-rock piles are compositionally different from the younger Sugar Shack South, Sugar Shack Middle, and Old Sulphur Gulch piles. The Capulin and Sugar Shack West piles have the lowest-pH leachates (pH 3.0-4.1) of the waste-pile samples, and the source material for the Capulin and Sugar Shack West piles appears to be similar to the source material for the erosional-scar areas. Calcite dissolution, in addition to gypsum dissolution, appears to produce the calcium and sulfate concentrations in leachates from the Sugar Shack South, Sugar Shack Middle, and Old Sulphur Gulch piles.

Smith, Kathleen S.; Hageman, Philip L.; Briggs, Paul H.; Sutley, Stephen J.; McCleskey, R. Blaine; Livo, K. Eric; Verplanck, Philip L.; Adams, Monique G.; Gemery-Hill, Pamela A.

2007-01-01

147

Composite material including nanocrystals and methods of making  

SciTech Connect

Temperature-sensing compositions can include an inorganic material, such as a semiconductor nanocrystal. The nanocrystal can be a dependable and accurate indicator of temperature. The intensity of emission of the nanocrystal varies with temperature and can be highly sensitive to surface temperature. The nanocrystals can be processed with a binder to form a matrix, which can be varied by altering the chemical nature of the surface of the nanocrystal. A nanocrystal with a compatibilizing outer layer can be incorporated into a coating formulation and retain its temperature sensitive emissive properties

Bawendi, Moungi G. (Boston, MA); Sundar, Vikram C. (New York, NY)

2008-02-05

148

APPLICATION OF ELECTROLESS METAL DEPOSITION FOR ADVANCED COMPOSITE SHIELDING MATERIALS  

Microsoft Academic Search

This paper presents the principles of formation and properties of new fibre composite materials for electromagnetic shields. Composite fibres consist of organic basis and metallic particles formed on surface and in the volume of fibre using electroless deposition technology. Polyacrylonitrile was the main type of fibres material that employed for modification and creation of composite structure. Polymer-like transformation of polyacrylonitrile

V. Bogush

149

Composite materials: Tomorrow for the day after tomorrow  

NASA Technical Reports Server (NTRS)

A description is given of the history of the use of composite materials in the aerospace industry. Research programs underway to obtain exact data on the behavior of composite materials over time are discussed. It is concluded that metal composites have not yet replaced metals, but that that this may be a future possibility.

Condom, P.

1982-01-01

150

Review on advanced composite materials boring mechanism and tools  

Microsoft Academic Search

With the rapid development of aviation and aerospace manufacturing technology, advanced composite materials represented by carbon fibre reinforced plastics (CFRP) and super hybrid composites (fibre\\/metal plates) are more and more widely applied. The fibres are mainly carbon fibre, boron fibre, Aramid fiber and Sic fibre. The matrixes are resin matrix, metal matrix and ceramic matrix. Advanced composite materials have higher

Runping Shi; Chengyong Wang

2010-01-01

151

Method of preparing corrosion resistant composite materials  

DOEpatents

Method of manufacture of ceramic materials which require stability in severely-corrosive environment having high alkali-metal activity, high sulfur/sulfide activity and/or molten halides at temperatures of 200.degree.-550.degree. C. or organic salt (including SO.sub.2 and SO.sub.2 Cl.sub.2) at temperatures of 25.degree.-200.degree. C. These surfide ceramics form stoichiometric (single-phase) compounds with sulfides of Ca, Li, Na, K, Al, Mg, Si, Y, La, Ce, Ga, Ba, Zr and Sr and show melting-points that are sufficiently low and have excellent wettability with many metals (Fe, Ni, Mo) to easily form metal/ceramic seals. Ceramic compositions are also formulated to adequately match thermal expansion coefficient of adjacent metal components.

Kaun, Thomas D. (320 Willow St., New Lenox, IL 60451)

1993-01-01

152

On the contribution of natural and restored wetlands to changes in the concentration and composition of dissolved organic material in the Sacramento-San Joaquin Delta and San Francisco Estuary.  

NASA Astrophysics Data System (ADS)

The amount and quality of wetland-derived dissolved organic material (DOM) entering delta and estuary environments remains poorly characterized even though DOM has two roles of societal significance: 1) it supports estuarine foodwebs, commonly habitat for endangered species, and 2) it presents problems when it occurs in drinking water supplies, forming carcinogenic byproducts on treatment. The Sacramento-San Joaquin Delta is a source of drinking water for over 20 million people and contributes 80% of the DOM entering the San Francisco Estuary, nearly doubling the concentration of DOM in the influent river water. The majority of the Delta is composed of below-sea level peat islands maintained in agricultural production by continuous pumping of DOM-rich drain water into Delta channels. Previous studies have shown that changes in the composition of the DOM in water that passes through the Delta are not consistent with addition of peat island drain water, and are more consistent with addition of wetland-derived material, suggesting that wetlands may contribute substantially to DOM export to the Estuary. Although wetlands currently contribute only 14% of the Delta, restoration is planned that would more than double this area, potentially altering DOM quality and content in the Delta and Estuary waters. Over the past several years we have examined the seasonal variation in the quality of DOM added by a variety of wetland types and island drains within the Delta and Estuary. In the current study, thirteen sites were each sampled five times. To date, we have analyzed the samples to determine the content of hydrophobic DOM, characterize the UV absorbance and fluorescence properties, and quantify the susceptibility to biodegradation both before and after photo-exposure. Samples were humic-rich, averaging over 75% hydrophobic content and varying from 74 to 86% with the variation in hydrophobic content between samples corresponding to changes in the optical properties. Samples typically were refractory with respect to biodegradation, with an average of 11% of the DOM susceptible to biodegradation prior to photoexposure, but the range was from 1% to 48%. Following photoexposure, samples were generally more refractory rather than more labile. Wetland DOM was found to react to form more drinking water disinfection byproducts than influent waters, but some wetland types appeared to contribute fewer precursors. Seasonal variation in biodegradation and chemical parameters was much greater than variation among wetland types, and the peak of biodegradeability was not related to the seasonal peak in DOM. This suggests addition of DOM through the Delta is controlled by changes in the nature of the source material rather than changes in efficiency or extent of remineralization.

Bergamaschi, B.; Stepanauskas, R.; Fram, M.; Hollibaugh, J.; Fujii, R.

2002-12-01

153

Lightweight Impact-Resistant Composite Materials: Lessons from Mantis Shrimp  

NASA Astrophysics Data System (ADS)

Nature has evolved efficient strategies to synthesize complex mineralized structures that exhibit exceptional damage tolerance. One such example is found in the hyper-mineralized hammer-like dactyl clubs of the stomatopods, a group of highly aggressive marine crustaceans. The dactyl clubs from one such species, Odontodactylus Scyllarus, exhibit an impressive set of characteristics adapted for surviving high velocity impacts with the heavily mineralized prey species on which they feed. Consisting of a multi-phase composite of oriented crystalline hydroxyapatite and amorphous calcium phosphate and carbonate, in conjunction with a highly expanded helicoidal organization of the fibrillar chitinous organic matrix, these structures display several effective lines of defense against catastrophic failure during repetitive high energy loading events. The study of this organism and its relatives has lead to design cues, which were incorporated into prototype composite materials designed for applications in aviation, body armor, and entertainment.

Milliron, Garrett Wayne

154

High strain rate effects for composite materials  

SciTech Connect

We have been developing the capability to characterize the high strain rate response of continuous fiber polymer composites. The data presented covers strain rates from 0/sec to 3000/sec. A combination of test machines and specimen geometries was investigated. Strain rates from 0--100/sec were generated using conventional and high speed hydraulic test machines. Strain rates from 10--1000/sec were generated using a high energy drop tower, and rates from 1000--3000/sec were generated using a split Hopkinson bar. Strain rates above 100/sec have only been generated for uniaxial compression. Our efforts have primarily focused on developing the high energy drop tower for these purposes. Specimen geometries for compression include tapered cubes, one inch tubes, and solid rods. For tension a smaller 0.5 in. diameter version of our 2.0 in. diameter multiaxial test specimen was developed and has been successfully used at strain rates up to 100 per second. Fixtures were also developed for performing high strain rate shear testing and through thickness penetration studies of composite plates. The objective of these experiments is to develop dynamic material models for use in finite element design tools. This presentation will focus on the methods and results obtained from this study.

Groves, S.E.; Sanchez, R.J.; Lyon, R.E.; Brown, A.E.

1992-04-16

155

Method for preparing polyolefin composites containing a phase change material  

DOEpatents

A composite useful in thermal energy storage, said composite being formed of a polyolefin matrix having a phase change material such as a crystalline alkyl hydrocarbon incorporated therein. The composite is useful in forming pellets, sheets or fibers having thermal energy storage characteristics; methods for forming the composite are also disclosed.

Salyer, Ival O. (Dayton, OH)

1990-01-01

156

Natural materials for nano bio systems  

NASA Astrophysics Data System (ADS)

Many papers have been published on the properties of deoxyribonucleic acid (DNA) and DNAhexadecyltrimethylammonium chloride (CTMA) and their applications in electronics and photonics. This paper is a review of some of the properties and their related applications for other types of naturally occurring materials, nucleic acid bases or nucleobases which make up the DNA molecules. Nucleobases under investigation included guanine, cytosine, adenine and thymine. Potential applications include electron blocking layers for organic light emitting diodes, gate dielectrics for organic thin film transistors and protective layers for polymer-based capacitors.

Ouchen, Fahima; Yaney, Perry; Joyce, Donna; Williams, Adrienne; Gomez, Eliot; Subramanyam, Guru; Grote, James

2014-09-01

157

Separating Mixtures: How We Concentrate Natural Materials  

NSDL National Science Digital Library

This activity involves separating mixtures of minerals on the basis of their physical properties. Students are shown a piece of granite and see that it is clearly a mixture. Students will try to devise ways of separating some simple mixtures and then see how some of the same methods are used to separate real minerals from mixtures. Students will discover that many useful materials are found as part of mixtures. For example, salt is found in underground deposits mixed with sand and clay. The mixture is called rock salt. Minerals are chemicals found naturally in the Earth and many of them are very useful. To get at the useful minerals, we usually have to separate them from less-useful material which are often called gangue (pronounced gang) by miners.

158

Designing nacre-like materials for simultaneous stiffness, strength and toughness: Optimum materials, composition, microstructure and size  

NASA Astrophysics Data System (ADS)

Nacre, bone and spider silk are staggered composites where inclusions of high aspect ratio reinforce a softer matrix. Such staggered composites have emerged through natural selection as the best configuration to produce stiffness, strength and toughness simultaneously. As a result, these remarkable materials are increasingly serving as model for synthetic composites with unusual and attractive performance. While several models have been developed to predict basic properties for biological and bio-inspired staggered composites, the designer is still left to struggle with finding optimum parameters. Unresolved issues include choosing optimum properties for inclusions and matrix, and resolving the contradictory effects of certain design variables. Here we overcome these difficulties with a multi-objective optimization for simultaneous high stiffness, strength and energy absorption in staggered composites. Our optimization scheme includes material properties for inclusions and matrix as design variables. This process reveals new guidelines, for example the staggered microstructure is only advantageous if the tablets are at least five times stronger than the interfaces, and only if high volume concentrations of tablets are used. We finally compile the results into a step-by-step optimization procedure which can be applied for the design of any type of high-performance staggered composite and at any length scale. The procedure produces optimum designs which are consistent with the materials and microstructure of natural nacre, confirming that this natural material is indeed optimized for mechanical performance.

Barthelat, Francois

2014-12-01

159

[NIR analysis of textile natural raw material].  

PubMed

NIR technology has gained more and more attention of researchers because of its advantage of simplicity, quickness and non destructive property of detection. And combined with chemometrics method, it could remedy some disadvantages such as overlapping of peaks and feebleness of information. Now, NIR has been applied in many fields such as medicine and chemical industry. Textile is an important part in human life. With the development of society, people pay more attention to this field. Using microscope to discriminate textile fibre by man and using solution method to detect content of fibre are two main detection methods in textile national standards. These methods of discrimination demand a lot of training and practical experience. At the same time, many artificial factors in the process may result in different examination results of the same sample. In addition, they are time-consuming (6 hours on average) and not suitable for large quantity of sample detection. Therefore, doubtless finding another more quickly and nondestructive way to complete detection of textile fibre makes great sense. Compared with microscope method and chemical method, NIR technical could decrease test time down to about 30 seconds. Because the structure of natural fibre is more complex than artificial fibre, NIR application in this field is much more difficult and demands more experience. So many researches were done by experts domestically and abroad in this field. The scope of these researches includes differentiation of foreign substance in natural fibre such as wool, cotton, and silk; prediction of natural fibre content such as residual grease content, mean fibre diameter (MFD) and moisture content. The present paper focuses mainly on the application of NIR in the textile industry, especially the analysis of textile natural raw material, including discrimination of natural fibre variety and detection of foreign fibre. PMID:19248487

Zhou, Ying; Xu, Hui-rong; Ying, Yi-bin

2008-12-01

160

CCMR: â Green â Composites: An alternative to petroleum-based materials  

NSDL National Science Digital Library

Composites made from natural fibers and resins offer a potential alternative to the petroleum-based materials that are currently used in in many applications such as packaging. These composites have the advantage of being biodegradable, renewable and environmentally friendly. In this work, different additives, including glycerol and polycarboxylic acid (PCA), are introduced to these composites in an attempt to increase properties such as strength and flexibility.

Cooley, Ladean M.

2007-08-29

161

Processing and characterization of natural cellulose fibers/thermoset polymer composites.  

PubMed

Recently natural cellulose fibers from different biorenewable resources have attracted the considerable attraction of research community all around the globe owing to their unique intrinsic properties such as biodegradability, easy availability, environmental friendliness, flexibility, easy processing and impressive physico-mechanical properties. Natural cellulose fibers based materials are finding their applications in a number of fields ranging from automotive to biomedical. Natural cellulose fibers have been frequently used as the reinforcement component in polymers to add the specific properties in the final product. A variety of cellulose fibers based polymer composite materials have been developed using various synthetic strategies. Seeing the immense advantages of cellulose fibers, in this article we discuss the processing of biorenewable natural cellulose fibers; chemical functionalization of cellulose fibers; synthesis of polymer resins; different strategies to prepare cellulose based green polymer composites, and diverse applications of natural cellulose fibers/polymer composite materials. The article provides an in depth analysis and comprehensive knowledge to the beginners in the field of natural cellulose fibers/polymer composites. The prime aim of this review article is to demonstrate the recent development and emerging applications of natural cellulose fibers and their polymer materials. PMID:24815407

Thakur, Vijay Kumar; Thakur, Manju Kumari

2014-08-30

162

Photochromism in composite and hybrid materials based on transition-metal oxides and polyoxometalates  

Microsoft Academic Search

Photochromic materials are attractive and promising for applications in many fields. One subject in this area is to prepare and study the photochromism in composite or hybrid materials based on transition-metal oxides or polyoxometalates. Their properties not depend only on the chemical nature of each component, but also on the interface and synergy between them. Since the charge transfer plays

Tao He; Jiannian Yao

2006-01-01

163

Some functional properties of composite material based on scrap tires  

NASA Astrophysics Data System (ADS)

The utilization of scrap tires still obtains a remarkable importance from the aspect of unloading the environment from non-degradable waste [1]. One of the most prospective ways for scrap tires reuse is a production of composite materials [2] This research must be considered as a continuation of previous investigations [3, 4]. It is devoted to the clarification of some functional properties, which are considered important for the view of practical applications, of the composite material. Some functional properties of the material were investigated, for instance, the compressive stress at different extent of deformation of sample (till 67% of initial thickness) (LVS EN 826) [5] and the resistance to UV radiation (modified method based on LVS EN 14836) [6]. Experiments were realized on the purposefully selected samples. The results were evaluated in the correlation with potential changes of Shore C hardness (Shore scale, ISO 7619-1, ISO 868) [7, 8]. The results showed noticeable resistance of the composite material against the mechanical influence and ultraviolet (UV) radiation. The correlation with the composition of the material, activity of binder, definite technological parameters, and the conditions supported during the production, were determined. It was estimated that selected properties and characteristics of the material are strongly dependent from the composition and technological parameters used in production of the composite material, and from the size of rubber crumb. Obtained results show possibility to attain desirable changes in the composite material properties by changing both the composition and technological parameters of examined material.

Plesuma, Renate; Malers, Laimonis

2013-09-01

164

Natural Cork Agglomerate Employed as an Environmentally Friendly Solution for Quiet Sandwich Composites  

PubMed Central

Carbon fiber-synthetic foam core sandwich composites are widely used for many structural applications due to their superior mechanical performance and low weight. Unfortunately these structures typically have very poor acoustic performance. There is increasingly growing demand in mitigating this noise issue in sandwich composite structures. This study shows that marrying carbon fiber composites with natural cork in a sandwich structure provides a synergistic effect yielding a noise-free sandwich composite structure without the sacrifice of mechanical performance or weight. Moreover the cork-core sandwich composites boast a 250% improvement in damping performance, providing increased durability and lifetime operation. Additionally as the world seeks environmentally friendly materials, the harvesting of cork is a natural, renewable process which reduces subsequent carbon footprints. Such a transition from synthetic foam cores to natural cork cores could provide unprecedented improvements in acoustic and vibrational performance in applications such as aircraft cabins or wind turbine blades. PMID:22574250

Sargianis, James; Kim, Hyung-ick; Suhr, Jonghwan

2012-01-01

165

Natural cork agglomerate employed as an environmentally friendly solution for quiet sandwich composites.  

PubMed

Carbon fiber-synthetic foam core sandwich composites are widely used for many structural applications due to their superior mechanical performance and low weight. Unfortunately these structures typically have very poor acoustic performance. There is increasingly growing demand in mitigating this noise issue in sandwich composite structures. This study shows that marrying carbon fiber composites with natural cork in a sandwich structure provides a synergistic effect yielding a noise-free sandwich composite structure without the sacrifice of mechanical performance or weight. Moreover the cork-core sandwich composites boast a 250% improvement in damping performance, providing increased durability and lifetime operation. Additionally as the world seeks environmentally friendly materials, the harvesting of cork is a natural, renewable process which reduces subsequent carbon footprints. Such a transition from synthetic foam cores to natural cork cores could provide unprecedented improvements in acoustic and vibrational performance in applications such as aircraft cabins or wind turbine blades. PMID:22574250

Sargianis, James; Kim, Hyung-ick; Suhr, Jonghwan

2012-01-01

166

Nature of branching in disordered materials  

NASA Astrophysics Data System (ADS)

The phenomenon of structural branching is ubiquitous in a wide array of materials such as polymers, ceramic aggregates, networks and gels. These materials with structural branching are a unique class of disordered materials and often display complex architectures. Branching has a strong influence over the structure-property relationships of these materials. Despite the generic importance across a wide spectrum of materials, our physical understanding of the scientific nature of branching and the analytic description and quantification of branching is at an early stage, though many decades of effort have been made. For polymers, branching is conventionally characterized by hydrodynamic radius (size exclusion chromatography, SEC, rheology) or by counting branch sites (nuclear magnetic resonance spectroscopy, NMR). SEC and rheology are, at best, qualitative; and quantitative characterization techniques like NMR and transmission electron microscopy (TEM) (for ceramic nanoparticulate aggregates) have limitations in providing routine quantification. Effective structure characterization, though an important step in understanding these materials, remains elusive. For ceramic aggregates, theoretical work has dominated and only a few publications on analytic studies exist to support theory. A new generic scaling model is proposed in Chapter I, which encompasses the critical structural features associated with these complex architectures. The central theme of this work is the application of this model to describe a variety of disordered structures like aggregated nano-particulates, long chain branched polymers like polyethylene, hyperbranched polymers, multi-arm star polymers, and cyclic macromolecules. The application of the proposed model to these materials results in a number of fundamental structural parameters, like the mass-fractal dimension, df, the minimum path dimension, dmin, connectivity dimension, c, and the mole fraction branch content, ?br. These dimensions reflect different features of the global structure, and it is categorically shown that this dimensional analysis results in effective structure characterization of these materials. Small-angle scattering of x-rays and neutrons can be used to quantify branch content and characterize the structure, through application of concepts native to fractal geometry. The application of the scaling model to nano-particulate aggregates yields quantitative information regarding the structure of these materials. In-situ small and ultra small angle x-ray scattering data collected on fumed silica and soot particles is presented in Chapter II. These measurements were performed at Advanced Photon Source, Argonne National Laboratory, UNICAT beam-line and the European Synchrotron Radiation Facility, Grenoble, France, ID2 beam-line. The dimensional analysis is successful in not only giving an average snap-shot of the nano-particulate aggregates, but also yields information regarding the growth processes involved in the complex pyrolysis technique of synthesizing these materials. In case of macromolecular systems, the minimum path dimension, dmin, is shown to reflect the thermodynamics of the system. This is categorically established in Chapter III on hyperbranched polymers, where the scaling model accurately predicts the good-solvent to theta-condition transition in these highly branched polymers with increasing molar mass. The scaling model is applied to the long standing problem of quantifying long chain branching in polyethylene in Chapter IV. Small angle neutron scattering data on dilute solutions of polyethylene were obtained at the Intense Pulsed Neutron Source (SAND beam-line); NIST center for Neutron Scattering (NG3 beam-line); and Los Alamos Neutron Scattering Center (LQD beam-line). This work, for the first time in literature, reports the length of a long chain branch in polyethylene in terms of the average molar mass of the branches, and the average number of carbon atoms in the long chain branch. Cyclic polymers are examined in the Chapter V. The scaling model presents a new

Kulkarni, Amit S.

167

Controlled intermittent interfacial bond concept for composite materials  

NASA Technical Reports Server (NTRS)

Concept will enhance fracture resistance of high-strength filamentary composite without degrading its tensile strength or elastic modulus. Concept provides more economical composite systems, tailored for specific applications, and composite materials with mechanical properties, such as tensile strength, fracture strain, and fracture toughness, that can be optimized.

Marston, T. U.; Atkins, A. G.

1975-01-01

168

Cytotoxic and mutagenic effects of dental composite materials  

Microsoft Academic Search

Mutagenicity of single compounds of dental resinous materials has been investigated on many occasions before, but the induction of mutagenic effects by extracts of clinically used composites is still unknown. Here, cytotoxic effects and the formation of micronuclei were determined in V79 fibroblasts after exposure to extracts of modern composite filling materials (Solitaire, Solitaire 2, Tetric Ceram, Dyract AP, Definite).

Helmut Schweikl; Karl-Anton Hiller; Carola Bolay; Marion Kreissl; Wetscheslaw Kreismann; Agathe Nusser; Stefanie Steinhauser; Janusz Wieczorek; Rudolf Vasold; Gottfried Schmalz

2005-01-01

169

Industry technology assessment of graphite-polymide composite materials. [conferences  

NASA Technical Reports Server (NTRS)

An assessment of the current state of the art and the future prospects for graphite polyimide composite material technology is presented. Presentations and discussions given at a minisymposium of major issues on the present and future use, availability, processing, manufacturing, and testing of graphite polyimide composite materials are summarized.

1975-01-01

170

Pistons and Cylinders Made of Carbon-Carbon Composite Materials  

NASA Technical Reports Server (NTRS)

An improved reciprocating internal combustion engine has a plurality of engine pistons, which are fabricated from carbon---carbon composite materials, in operative association with an engine cylinder block, or an engine cylinder tube, or an engine cylinder jug, all of which are also fabricated from carbon-carbon composite materials.

Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor); Schwind, Francis A. (Inventor)

2000-01-01

171

Pistons and Cylinders Made of Carbon-Carbon Composite Materials  

NASA Technical Reports Server (NTRS)

An improved reciprocating internal combustion engine has a plurality of engine pistons, which are fabricated from carbon-carbon composite materials, in operative association with an engine cylinder block, or an engine cylinder tube, or an engine cylinder jug, all of which are also fabricated from carbon-carbon composite materials.

Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor); Schwind, Francis A. (Inventor)

2000-01-01

172

Characterization of a High Strain Composite Material I. Maqueda  

E-print Network

Characterization of a High Strain Composite Material I. Maqueda and S. Pellegrino California and developed a high-strain composite material consisting of car- bon fibers embedded in a silicone matrix that localize the high-strain capability in narrow regions of a structure, so that elastic fold lines are formed

Pellegrino, Sergio

173

Orthotic devices using lightweight composite materials  

NASA Technical Reports Server (NTRS)

Potential applications of high strength, lightweight composite technology in the orthotic field were studied. Several devices were designed and fabricated using graphite-epoxy composite technology. Devices included shoe plates, assistive walker devices, and a Simes prosthesis reinforcement. Several other projects having medical application were investigated and evaluations were made of the potential for use of composite technology. A seat assembly was fabricated using sandwich construction techniques for the Total Wheelchair Project.

Harrison, E., Jr.

1983-01-01

174

Advanced organic composite materials for aircraft structures: Future program  

NASA Technical Reports Server (NTRS)

Revolutionary advances in structural materials have been responsible for revolutionary changes in all fields of engineering. These advances have had and are still having a significant impact on aircraft design and performance. Composites are engineered materials. Their properties are tailored through the use of a mix or blend of different constituents to maximize selected properties of strength and/or stiffness at reduced weights. More than 20 years have passed since the potentials of filamentary composite materials were identified. During the 1970s much lower cost carbon filaments became a reality and gradually designers turned from boron to carbon composites. Despite progress in this field, filamentary composites still have significant unfulfilled potential for increasing aircraft productivity; the rendering of advanced organic composite materials into production aircraft structures was disappointingly slow. Why this is and research and technology development actions that will assist in accelerating the application of advanced organic composites to production aircraft is discussed.

1987-01-01

175

Material, process, and product design of thermoplastic composite materials  

NASA Astrophysics Data System (ADS)

Thermoplastic composites made of polypropylene (PP) and E-glass fibers were investigated experimentally as well as theoretically for two new classes of product designs. The first application was for reinforcement of wood. Commingled PP/glass yarn was consolidated and bonded on wood panel using a tie layer. The processing parameters, including temperature, pressure, heating time, cooling time, bonding strength, and bending strength were tested experimentally and evaluated analytically. The thermoplastic adhesive interface was investigated with environmental scanning electron microscopy. The wood/composite structural design was optimized and evaluated using a Graphic Method. In the second application, we evaluated use of thermoplastic composites for explosion containment in an arrester. PP/glass yarn was fabricated in a sleeve form and wrapped around the arrester. After consolidation, the flexible composite sleeve forms a solid composite shell. The composite shell acts as a protection layer in a surge test to contain the fragments of the arrester. The manufacturing process for forming the composite shell was designed. Woven, knitted, and braided textile composite shells made of commingled PP/glass yarn were tested and evaluated. Mechanical performance of the woven, knitted, and braided composite shells was examined analytically. The theoretical predictions were used to verify the experimental results.

Dai, Heming

176

The potential leachability from natural road construction materials  

Microsoft Academic Search

Leaching characteristics are used for the evaluation of waste materials in road construction. Few leaching tests have been performed on natural rock materials which implies that there is a lack of data to be used in comparison with waste materials. In order to form a basis for comparison of the leachability, nine natural road construction materials in Sweden were investigated

Mia Tossavainen; Eric Forssberg

1999-01-01

177

Application of advanced material systems to composite frame elements  

NASA Technical Reports Server (NTRS)

A three phase program has been conducted to investigate DuPont's Long Discontinuous Fiber (LDF) composites. Additional tests were conducted to compare LDF composites against toughened thermosets and a baseline thermoset system. Results have shown that the LDF AS4/PEKK offers improved interlaminar (flange bending) strength with little reduction in mechanical properties due to the discontinuous nature of the fibers. In the third phase, a series of AS4/PEKK LDF C-section curved frames (representing a typical rotorcraft light frame) were designed, manufactured and tested. Specimen reconsolidation after 'stretch forming' and frame thickness were found to be key factors in this light frame's performance. A finite element model was constructed to correlate frame test results with expected strain levels determined from material property tests. Adequately reconsolidated frames performed well and failed at strain levels at or above baseline thermoset material test strains. Finally a cost study was conducted which has shown that the use of LDF for this frame would result in a significant cost savings, for moderate to large lot sizes compared with the hand lay-up of a thermoset frame.

Llorente, Steven; Minguet, Pierre; Fay, Russell; Medwin, Steven

1992-01-01

178

Local Debonding and Fiber Breakage in Composite Materials Modeled Accurately  

NASA Technical Reports Server (NTRS)

A prerequisite for full utilization of composite materials in aerospace components is accurate design and life prediction tools that enable the assessment of component performance and reliability. Such tools assist both structural analysts, who design and optimize structures composed of composite materials, and materials scientists who design and optimize the composite materials themselves. NASA Glenn Research Center's Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC) software package (http://www.grc.nasa.gov/WWW/LPB/mac) addresses this need for composite design and life prediction tools by providing a widely applicable and accurate approach to modeling composite materials. Furthermore, MAC/GMC serves as a platform for incorporating new local models and capabilities that are under development at NASA, thus enabling these new capabilities to progress rapidly to a stage in which they can be employed by the code's end users.

Bednarcyk, Brett A.; Arnold, Steven M.

2001-01-01

179

Study of composites as substrate materials in large space telescopes  

NASA Technical Reports Server (NTRS)

Nonmetallic composites such as the graphite/epoxy system were investigated as possible substrates for the primary mirror of the large space telescope. The possible use of fiber reinforced metal matrix composites was reviewed in the literature. Problems arising out of the use of composites as substrate materials such as grinding, polishing, adherence of reflective coatings, rigidity of substrate, hygrospcopici tendency of the composites, thermal and temporal stability and other related problems were examined.

Sharma, A. V.

1979-01-01

180

Flexible hydrogel-based functional composite materials  

DOEpatents

A composite having a flexible hydrogel polymer formed by mixing an organic phase with an inorganic composition, the organic phase selected from the group consisting of a hydrogel monomer, a crosslinker, a radical initiator, and/or a solvent. A polymerization mixture is formed and polymerized into a desired shape and size.

2013-10-08

181

Corrosion inhibiting composition for treating asbestos containing materials  

DOEpatents

A composition for transforming a chrysotile asbestos-containing material into a non-asbestos material is disclosed, wherein the composition comprises water, at least about 30% by weight of an acid component, optionally a source of fluoride ions, and a corrosion inhibiting amount of thiourea, a lower alkylthiourea, a C.sub.8 -C.sub.15 alkylpyridinium halide or mixtures thereof. A method of transforming an asbestos-containing building material, while part of a building structure, into a non-asbestos material by using the present composition also is disclosed.

Hartman, Judithann Ruth (Columbia, MD)

1998-04-21

182

Corrosion inhibiting composition for treating asbestos containing materials  

DOEpatents

A composition for transforming a chrysotile asbestos-containing material into a non-asbestos material is disclosed. The composition comprises water, at least about 30% by weight of an acid component, optionally a source of fluoride ions, and a corrosion inhibiting amount of thiourea, a lower alkylthiourea, a C{sub 8}{single_bond}C{sub 15} alkylpyridinium halide or mixtures. A method of transforming an asbestos-containing building material, while part of a building structure, into a non-asbestos material by using the present composition also is disclosed.

Hartman, J.R.

1998-04-21

183

Active composite materials as sensing elements for fiber-reinforced smart composite structures  

NASA Astrophysics Data System (ADS)

Polymer based piezoelectric composite materials can be readily integrated within laminated composite structures to provide sensing and actuating capabilities. In this study composite films of ferroelectric ceramic/polymer materials have been developed and characterized as in-situ multi purpose sensing elements for the nondestructive monitoring of fiber reinforced composites. In this paper the response of embedded composite films to simulated acoustic emission signals will be presented and discussed. Results show the ability of the composite sensors to detect signals from acoustic emission sources over a wide bandwidth.

Blanas, Panagiotis; Wenger, Matthew P.; Rigas, Elias J.; Das-Gupta, Dilip K.

1998-07-01

184

About composite materials and their use in bone surgery.  

PubMed

Composite materials consist of two or even more different material components or phases, which are combined with the aim to improve physical, mechanical and/or biological properties. Such structures are designed to fulfil very specific requirements with respect to a selected device application making full use of their higher weight-specific strength and/or stiffness. Furthermore, these materials offer an opportunity for constructing radiolucent devices. In medical technology, composite materials mainly consist of a polymer matrix and fibres as a reinforcement phase. Composites similar to those known from technical applications reveal a number of specific biological problems. This is due to the materials and manufacturing processes available for the construction of such composites preventing their unrestricted use in direct bone contact. Nevertheless, an application potential for these materials in bone surgery exists and justifies further research and development efforts. PMID:11270081

Gasser, B

2000-12-01

185

Multilayer composite material and method for evaporative cooling  

NASA Technical Reports Server (NTRS)

A multilayer composite material and method for evaporative cooling of a person employs an evaporative cooling liquid that changes phase from a liquid to a gaseous state to absorb thermal energy. The evaporative cooling liquid is absorbed into a superabsorbent material enclosed within the multilayer composite material. The multilayer composite material has a high percentage of the evaporative cooling liquid in the matrix. The cooling effect can be sustained for an extended period of time because of the high percentage of phase change liquid that can be absorbed into the superabsorbent. Such a composite can be used for cooling febrile patients by evaporative cooling as the evaporative cooling liquid in the matrix changes from a liquid to a gaseous state to absorb thermal energy. The composite can be made with a perforated barrier material around the outside to regulate the evaporation rate of the phase change liquid. Alternatively, the composite can be made with an imperveous barrier material or semipermeable membrane on one side to prevent the liquid from contacting the person's skin. The evaporative cooling liquid in the matrix can be recharged by soaking the material in the liquid. The multilayer composite material can be fashioned into blankets, garments and other articles.

Buckley, Theresa M. (Inventor)

2002-01-01

186

School of Mechanical and Materials Engineering Composites Materials and Engineering Center  

E-print Network

and manufacturing technologies from a range of recycled and renewable resources. In 2015, CMEC will join other WSU and bio-based composite materials and sustainable manufacturing processes and design; ability to seekSchool of Mechanical and Materials Engineering and Composites Materials and Engineering Center

Collins, Gary S.

187

Nano composite phase change materials microcapsules  

NASA Astrophysics Data System (ADS)

MicroPCMs with nano composite structures (NC-MicroPCMs) have been systematically studied. NC-MicroPCMs were fabricated by the in situ polymerization and addition of silver NPs into core-shell structures. A full factorial experiment was designed, including three factors of core/shell, molar ratio of formaldehyde/melamine and NPs addition. 12 MicroPCMs samples were prepared. The encapsulated efficiency is approximately 80% to 90%. The structural/morphological features of the NC-MicroPCMs were evaluated. The size was in a range of 3.4 mu m to 4.0 mu m. The coarse appearance is attributed to NPs and NPs are distributed on the surface, within the shell and core. The NC-MicroPCMs contain new chemical components and molecular groups, due to the formation of chemical bonds after the pretreatment of NPs. Extra X-ray diffraction peaks of silver were found indicating silver nano-particles were formed into an integral structure with the core/shell structure by means of chemical bonds and physical linkages. Extra functionalities were found, including: (1) enhancement of IR radiation properties; (2) depression of super-cooling, and (3) increase of thermal stabilities. The effects of SERS (Surface Enhanced Raman Spectroscopy) arising from the silver nano-particles were observed. The Raman scattering intensity was magnified more than 100 times. These effects were also exhibited in macroscopic level in the fabric coatings as enhanced IR radiation properties were detected by the "Fabric Infrared Radiation Management Tester" (FRMT). "Degree of Crystallinity" (DOC) was measured and found the three factors have a strong influence on it. DOC is closely related to thermal stability and MicroPCMs with a higher DOC show better temperature resistance. The thermal regulating effects of the MicroPCMs coatings were studied. A "plateau regions" was detected around the temperature of phase change, showing the function of PCMs. Addition of silver nano-particles to the MicroPCMs has a positive influence on it. NC-MicroPCMs with introducing silver nano particles into the MicroPCMs structure, have shown excellent multifunctional thermal properties and thermal stabilities that are far beyond those of the conventional MicroPCMs. The novel NC-MicroPCMs can be used to develop advanced smart materials and products with prosperous and promising applications in a number of industries.

Song, Qingwen

188

Reflection and transmission for layered composite materials  

NASA Technical Reports Server (NTRS)

A layered planar structure consisting of different bianisotropic materials separated by jump-immittance sheets is considered. Reflection and transmission coefficients are determined via a chain-matrix algorithm. Applications are important for radomes and radar-absorbing materials.

Graglia, Roberto D.; Uslenghi, Piergiorgio L. E.

1991-01-01

189

Composite material application for liquid rocket engines  

NASA Technical Reports Server (NTRS)

With increasing emphasis on improving engine thrust-to-weight ratios to provide improved payload capabilities, weight reductions achievable by the use of composites have become attractive. Of primary significance is the weight reduction offered by composites, although high temperature properties and cost reduction were also considered. The potential for application of composites to components of Earth-to-orbit hydrocarbon engines and orbit-to-orbit LOX/H2 engines was assessed. The components most likely to benefit from the application of composites were identified, as were the critical technology areas where developed would be required. Recommendations were made and a program outlined for the design, fabrication, and demonstration of specific engine components.

Heubner, S. W.

1982-01-01

190

Fluid-induced vibration of composite natural gas pipelines  

Microsoft Academic Search

Advancements in materials bonding techniques have led to the use of reinforced composite pipelines. The use of steel pipe with a fiber-reinforced composite over-wrap together has produced an exceptionally strong pipe with positive advantages in weight and corrosion resistively. Understanding the dynamic characteristics of this kind of sub-sea composite pipelines, which often accommodate axial flow of gas, and prediction of

G. P. Zou; N. Cheraghi; F. Taheri

2005-01-01

191

Preparation of composite materials in space. Volume 1: Executive summary  

NASA Technical Reports Server (NTRS)

The reported objectives were to define promising materials, to obtain significant processing criteria and the related processing techniques and apparatus for the preparation of composites in space, and to establish a program for zero-g experiments and the required developmental efforts. Preparation was studied of the following composite types: (1) metal-base fiber and particle composites, including cemented compacts, (2) controlled density metals, comprising plain and reinforced metal foams, and (3) unidirectionally solidified eutectic alloys. The zero-g environment of orbital operations offers the capability to produce metal-base composite materials and castings which exhibit properties and, particularly, unique combinations of properties that cannot be achieved in terrestrial production.

Steurer, W. H.; Kaye, S.

1973-01-01

192

Prediction of natural frequency variability due to uncertainty in material properties  

NASA Technical Reports Server (NTRS)

Composite materials are widely used in various types of modern engineering structures. Traditional studies on composite structures have been based on the assumption that the material properties of the composites are characterized by a priori known elastic moduli, and no uncertainties of these moduli have been considered. However, the composite materials are invariably subject to a certain amount of scatter in their measured elastic moduli. To a large extent, the properties of composite materials are dependent on the fabrication process. But even the composite materials manufactured by the same process demonstrate differences in their elastic properties. This paper proposes a new, non-probabilistic method to predict the variability in the natural frequencies of the composite cylindrical shell, resulting from the unavoidable scatter in elastic moduli. The available measurements of elastic moduli are fitted by the four-dimensional uncertainty ellipsoid. The upper and lower bounds of the natural frequency are derived. With these bounds, designers will have a better understanding of the real dynamic behavior of the structure.

Li, Y. W.

1994-01-01

193

Production of composites by using gliadin as a bonding material  

Technology Transfer Automated Retrieval System (TEKTRAN)

In our previous papers, a new technology that produces biopolymer composites by particle-bonding was introduced. During the manufacturing process, micrometer-scale raw material was coated with a corn protein, zein, which is then processed to form a rigid material. The coating of raw-material particl...

194

Advanced composites: Fabrication processes for selected resin matrix materials  

NASA Technical Reports Server (NTRS)

This design note is based on present state of the art for epoxy and polyimide matrix composite fabrication technology. Boron/epoxy and polyimide and graphite/epoxy and polyimide structural parts can be successfully fabricated. Fabrication cycles for polyimide matrix composites have been shortened to near epoxy cycle times. Nondestructive testing has proven useful in detecting defects and anomalies in composite structure elements. Fabrication methods and tooling materials are discussed along with the advantages and disadvantages of different tooling materials. Types of honeycomb core, material costs and fabrication methods are shown in table form for comparison. Fabrication limits based on tooling size, pressure capabilities and various machining operations are also discussed.

Welhart, E. K.

1976-01-01

195

Preparation of composite materials in space. Volume 2: Technical report  

NASA Technical Reports Server (NTRS)

A study to define promising materials, significant processing criteria, and the related processing techniques and apparatus for the preparation of composite materials in space was conducted. The study also established a program for zero gravity experiments and the required developmental efforts. The following composite types were considered: (1) metal-base fiber and particle composites, including cemented compacts, (2) controlled density metals, comprising plain and reinforced metal foams, and (3) unidirectionally solidified eutectic alloys. A program of suborbital and orbital experiments for the 1972 to 1978 time period was established to identify materials, processes, and required experiment equipment.

Steurer, W. H.; Kaye, S.

1973-01-01

196

LDEF fiber-composite materials characterization  

NASA Technical Reports Server (NTRS)

Degradation of a number of fiber/polymer composites located on the leading and trailing surfaces of LDEF where the atomic oxygen (AO) fluences ranged from 10(exp 22) to 10(exp 4) atoms/cm(sup 2), respectively, was observed and compared. While matrices of the composites on the leading edge generally exhibited considerable degradation and erosion-induced fragmentation, this 'asking' process was confined to the near surface regions because these degraded structures acted as a 'protective blanket' for deeper-lying regions. This finding leads to the conclusion that simple surface coatings can significantly retard AO and other combinations of degrading phenomena in low-Earth orbit. Micrometeoroid and debris particle impacts were not a prominent feature on the fiber composites studied and apparently do not contribute in a significant way to their degradation or alteration in low-Earth orbit.

Miglionico, C. J.; Stein, C.; Roybal, R. E.; Murr, L. E.

1993-01-01

197

Processing of materials—monolithic to composites  

Microsoft Academic Search

A multimillion rupee 500-ton hydraulic extrusion\\/forging facility established at NPL, New Delhi, has been used to undertake\\u000a extensive studies in forming, the process of plastically deforming, which is the most important way of shaping materials.\\u000a Wrought materials are used extensively for making useful products employing extrusion and forging, the two important secondary\\u000a processing techniques used to convert materials into useful

Anil K Gupta

1995-01-01

198

Embedded electrode electro-optic composite materials  

NASA Astrophysics Data System (ADS)

We explore new concepts for electro-optic (EO) modulator designs based on local-field enhancement and electrodes in close proximity for improving the performance of nonlinear materials. Using nanopatterned metals or conductive materials for electrodes and plasmonic elements we show that the effective nonlinearity can be enhanced and concurrently the driving voltage reduced for electro-optic active materials. We especially devote our attention on EO modulator applications using polymers doped with active chromophores. Our substrate materials are mesoscopically patterned using focused ion beam milling. The critical dimensions of the features are smaller than a wavelength. The effective medium theory is used to analyze the results.

Nelson, Robert L.; Grote, James G.; Haus, Joseph W.; Birchfield, Brad

2006-08-01

199

Influence of thermal aging on crosslinking density of boron carbide\\/natural rubber composites  

Microsoft Academic Search

Composites of natural rubber and boron carbide with different concentrations were prepared as thermal neutron radiation shielding materials. The maximum degree of swelling (Q), the penetration rate (P) and the average diffusion coefficient (Dav) were studied. Using the Flory–Rehner equation, the crosslinking densities of the investigated samples were obtained. The effect of thermal oxidative aging on both the swelling behaviour

S. E. Gwaily; M. M. Badawy; H. H. Hassan; M. Madani

2003-01-01

200

Proc ACUN-5 "Developments in Composites: Advanced, Infrastructural, Natural and Nano-compsoites", UNSW, SYDNEY, Australia,  

E-print Network

Proc ACUN-5 "Developments in Composites: Advanced, Infrastructural, Natural and Nano-compsoites", UNSW, SYDNEY, Australia, 11-14 July 2006 High modulus carbon fiber materials for retrofit of steel_rizkalla@ncsu.edu Abstract This paper summarizes the research work dealing with the use of high modulus carbon fiber

201

Mechanical behaviour of composite materials made by resin film infusion  

NASA Astrophysics Data System (ADS)

Innovative composite materials are frequently used in designing aerospace, naval and automotive components. In the typical structure of composites, multiple layers are stacked together with a particular sequence in order to give specific mechanical properties. Layers are organized with different angles, different sequences and different technological process to obtain a new and innovative material. From the standpoint of engineering designer it is useful to consider the single layer of composite as macroscopically homogeneous material. However, composites are non homogeneous bodies. Moreover, layers are not often perfectly bonded together and delamination often occurs. Other violations of lamination theory hypotheses, such as plane stress and thin material, are not unusual and in many cases the transverse shear flexibility and the thickness-normal stiffness should be considered. Therefore the real behaviour of composite materials is quite different from the predictions coming from the traditional lamination theory. Due to the increasing structural performance required to innovative composites, the knowledge of the mechanical properties for different loading cases is a fundamental source of concern. Experimental characterization of materials and structures in different environmental conditions is extremely important to understand the mechanical behaviour of these new materials. The purpose of the present work is to characterize a composite material developed for aerospace applications and produced by means of the resin film infusion process (RFI). Different tests have been carried out: tensile, open-hole and filled-hole tensile, compressive, openhole and filled-hole compressive. The experimental campaign has the aim to define mechanical characteristics of this RFI composite material in different conditions: environmental temperature, Hot/Wet and Cold.

Barile, C.; Casavola, C.; Pappalettere, C.; Tursi, F.

2010-06-01

202

Health, safety and environmental requirements for composite materials  

NASA Technical Reports Server (NTRS)

The health, safety and environmental requirements for the production of composite materials are discussed. The areas covered include: (1) chemical identification for each chemical; (2) toxicology; (3) industrial hygiene; (4) fire and safety; (5) environmental aspects; and (6) medical concerns.

Hazer, Kathleen A.

1994-01-01

203

Effective pyroelectric response of compositionally graded ferroelectric materials  

E-print Network

in this range often must rely upon expensive cryogenically cooled semiconductor-based technology or utilize high--those materials being compositionally graded ferroelectric thin films formed from either potassium tantalum

Alpay, S. Pamir

204

Composite materials for thermal energy storage: enhancing performance through microstructures.  

PubMed

Chemical incompatibility and low thermal conductivity issues of molten-salt-based thermal energy storage materials can be addressed by using microstructured composites. Using a eutectic mixture of lithium and sodium carbonates as molten salt, magnesium oxide as supporting material, and graphite as thermal conductivity enhancer, the microstructural development, chemical compatibility, thermal stability, thermal conductivity, and thermal energy storage performance of composite materials are investigated. The ceramic supporting material is essential for preventing salt leakage and hence provides a solution to the chemical incompatibility issue. The use of graphite gives a significant enhancement on the thermal conductivity of the composite. Analyses suggest that the experimentally observed microstructural development of the composite is associated with the wettability of the salt on the ceramic substrate and that on the thermal conduction enhancer. PMID:24591286

Ge, Zhiwei; Ye, Feng; Ding, Yulong

2014-05-01

205

Space radiation effects on composite matrix materials - Analytical approaches  

NASA Technical Reports Server (NTRS)

In-vacuo ultraviolet and gamma radiation exposure tests are utilized in a study aimed at the identification of radiation damage mechanisms in composite materials, with the objective of predicting the long-term behavior of composite structures in a space environment at geosynchronous orbit. Physical and chemical methods of polymer characterization are utilized for the study of composite matrix degradation, in conjunction with GC/MS techniques for the analysis of volatile by-products.

Giori, C.

1979-01-01

206

The Effective Kerr Constant of an Electrooptical Composite Material  

Microsoft Academic Search

A general relationship is derived for the effective Kerr constant of an electrooptical composite material containing nonlinear centrosymmetric dielectric microcrystals; anisotropy of the inclusions and their nonsphericity were taken into account. It is shown that nonsphericity of the particles makes it possible to substantially enhance the Kerr constant of the composite in the case when the glass-matrix permittivity is much

A. A. Berezhnoi; M. I. Vasil'Ev; A. O. Volchek; A. V. Dotsenko; V. A. Tsekhomskii

2002-01-01

207

Joining and fabrication of metal-matrix composite materials  

NASA Technical Reports Server (NTRS)

Manufacturing technology associated with developing fabrication processes to incorporate metal-matrix composites into flight hardware is studied. The joining of composite to itself and to titanium by innovative brazing, diffusion bonding, and adhesive bonding is examined. The effects of the fabrication processes on the material properties and their influence on the design of YF-12 wing panels are discussed.

Royster, D. M.; Wiant, H. R.; Bales, T. T.

1975-01-01

208

Drilling carbon fiber-reinforced composite material at high speed  

Microsoft Academic Search

Increasing cutting speed will reduce machining time and hence improve productivity. Drilling is one of the most important cutting operations which are currently carried out on fiber-reinforced composites. Therefore, it is of interest to study the effects of increasing cutting speed on drilling characteristics of carbon fiber-reinforced composite materials. In this paper, the effects of increasing cutting speed ranging from

S. C. Lin; I. K. Chen

1996-01-01

209

Low-Cost Composite Materials and Structures for Aircraft Applications  

NASA Technical Reports Server (NTRS)

A survey of current applications of composite materials and structures in military, transport and General Aviation aircraft is presented to assess the maturity of composites technology, and the payoffs realized. The results of the survey show that performance requirements and the potential to reduce life cycle costs for military aircraft and direct operating costs for transport aircraft are the main reasons for the selection of composite materials for current aircraft applications. Initial acquisition costs of composite airframe components are affected by high material costs and complex certification tests which appear to discourage the widespread use of composite materials for aircraft applications. Material suppliers have performed very well to date in developing resin matrix and fiber systems for improved mechanical, durability and damage tolerance performance. The next challenge for material suppliers is to reduce material costs and to develop materials that are suitable for simplified and inexpensive manufacturing processes. The focus of airframe manufacturers should be on the development of structural designs that reduce assembly costs by the use of large-scale integration of airframe components with unitized structures and manufacturing processes that minimize excessive manual labor.

Deo, Ravi B.; Starnes, James H., Jr.; Holzwarth, Richard C.

2003-01-01

210

Semiempirical analysis of materials' elemental composition to formulate tissue-equivalent materials: a preliminary study  

NASA Astrophysics Data System (ADS)

Tissue-equivalent materials are used for simplifying quality control and quality assurance procedures, both in diagnostic and therapeutic radiology. Important information to formulate a tissue-equivalent material is elemental composition of its base materials. However, this information is not easily obtained. Therefore we propose a stoichiometric analysis method to investigate the elemental composition of the base materials that can potentially be used for manufacturing tissue-equivalent materials. In this technique, we combined the stoichiometric calibration and the basic data method to obtain the elemental composition of materials from measured computer tomography (CT) numbers. The elemental composition, with the maximum number of the elements of the material in question up to the available number of different tube voltages at the CT scanner, was analysed using the proposed approach. We tested eight different cylinders in this study. The estimated elemental compositions of unspecified materials in the cylinders were evaluated by comparing the calculated and the simulated CT numbers to the measured ones; the results showed good correlation with maximum absolute differences of 1.9 and 3.7 HU, respectively. The accuracy of the stoichiometric analysis method to estimate the elemental composition was influenced by the accuracy of the measured CT numbers. The method proposed allows for determining the elemental composition of the base materials which can then be applied further to formulate tissue-equivalent materials.

Yohannes, Indra; Kolditz, Daniel; Kalender, Willi A.

2011-05-01

211

Advanced Surface Laminar Circuit using new composite materials  

Microsoft Academic Search

This paper introduces a newly developed Advanced Surface Laminar Circuit (Adv-SLC) packaging technology, which utilizes new composite materials. Adv-SLC is a buildup substrate technology designed to satisfy the requirements of the most advanced semiconductor chips. We have developed a new dielectric material that is a build-up layer composed of two different materials. We also used a new material for the

Katsura Hayashi; Kimihiro Yamanaka; Kaoru Kobayashi; Yoshihiro Hosoi; Masahiro Fukui

2010-01-01

212

The composite nature of the $?(1520)$ resonance  

E-print Network

Recently, the Weinberg compositeness condition of a bound state was generalized to account for resonant states and higher partial waves. We apply this extension to the case of the $\\Lambda(1520)$ resonance and quantify the weight of the meson-baryon components in contrast to other possible genuine building blocks. This resonance was theoretically obtained from a coupled channels analysis using the s-waves $\\pi\\Sigma^*$, $K\\Xi^*$ and the d-waves $\\bar{K}N$ and $\\pi\\Sigma$ channels applying the techniques of the chiral unitary approach. We obtain that this resonance is essentially dynamically generated from these meson-baryon channels, leaving room for only $15 \\%$ weight of other kind of components into its wave function.

F. Aceti; E. Oset; L. Roca

2014-04-24

213

Composite nature of the ? (1520) resonance  

NASA Astrophysics Data System (ADS)

Recently, the Weinberg compositeness condition of a bound state was generalized to account for resonant states and higher partial waves. We apply this extension to the case of the ? (1520) resonance and quantify the weight of the meson-baryon components in contrast to other possible genuine building blocks. This resonance was theoretically obtained from a coupled channels analysis using the s-wave ??* and K? * and the d-wave K¯N and ?? channels, applying the techniques of the chiral unitary approach. We obtain the result that this resonance is essentially dynamically generated from these meson-baryon channels, leaving room for only 15% weight of other kinds of components in its wave function.

Aceti, F.; Oset, E.; Roca, L.

2014-08-01

214

Composite Materials for Radiation Shielding During Deep Space Missions  

NASA Technical Reports Server (NTRS)

Minimizing radiation exposure from the galactic cosmic ray (GCR) environment during deep space missions is essential to human health and sensitive instrument survivability. Given the fabrication constraints of space transportation vehicles protective shielding is, consequently, a complicated materials issue. These concerns are presented and considered in view of some novel composite materials being developed/suggested for GCR shielding applications. Advantages and disadvantages of the composites will be discussed as well as the need for coordinated testing/evaluation and modeling efforts.

Grugel, R. N.; Watts, J.; Adams, J. H.; Rose, M. Franklin (Technical Monitor)

2001-01-01

215

Finite element analysis of composites materials for aerospace applications  

Microsoft Academic Search

Composites materials are intended to be used more extensively as an alternative of aluminum structure in aircraft and aerospace applications. This is due to their attractive properties as high strength-to-weight ratio and stiffness-to-weight ratio. Besides that it clarifies the growing interest for composites materials due to advantages of lightweight, high strength, high stiffness, superior fatigue life, tremendous corrosion resistance and

M. Nurhaniza; M. K. A. Ariffin; Aidy Ali; F. Mustapha; A. W. Noraini

2010-01-01

216

Microstructure of composite material with powders of barium ferrite  

Microsoft Academic Search

Purpose: The aim of the present work is the microstructure characterization of commercial powder BaFe12O19 (as-prepared) and composite material with BaFe12O19 powders and polymer matrix, using XRD (X-Ray Diffraction) and SEM (Scanning Electron Microscopy) methods. Design\\/methodology\\/approach: The morphology of barium ferrite powders and a fracture surface of the examined composite material was realized by using the scanning electron microscope. The

R. Nowosielski; R. Babilas; G. Dercz; L. Paj?k b

217

Statistical analysis and interpolation of compositional data in materials science.  

PubMed

Compositional data are ubiquitous in chemistry and materials science: analysis of elements in multicomponent systems, combinatorial problems, etc., lead to data that are non-negative and sum to a constant (for example, atomic concentrations). The constant sum constraint restricts the sampling space to a simplex instead of the usual Euclidean space. Since statistical measures such as mean and standard deviation are defined for the Euclidean space, traditional correlation studies, multivariate analysis, and hypothesis testing may lead to erroneous dependencies and incorrect inferences when applied to compositional data. Furthermore, composition measurements that are used for data analytics may not include all of the elements contained in the material; that is, the measurements may be subcompositions of a higher-dimensional parent composition. Physically meaningful statistical analysis must yield results that are invariant under the number of composition elements, requiring the application of specialized statistical tools. We present specifics and subtleties of compositional data processing through discussion of illustrative examples. We introduce basic concepts, terminology, and methods required for the analysis of compositional data and utilize them for the spatial interpolation of composition in a sputtered thin film. The results demonstrate the importance of this mathematical framework for compositional data analysis (CDA) in the fields of materials science and chemistry. PMID:25547365

Pesenson, Misha Z; Suram, Santosh K; Gregoire, John M

2015-02-01

218

Digital cellular solids : reconfigurable composite materials  

E-print Network

Digital materials are comprised of a small number of types of discrete physical building blocks, which assemble to form constructions that meet the versatility and scalability of digital computation and communication ...

Cheung, Kenneth Chun-Wai

2012-01-01

219

High strain rate effects for composite materials  

Microsoft Academic Search

We have been developing the capability to characterize the high strain rate response of continuous fiber polymer composites. The data presented covers strain rates from 0\\/sec to 3000\\/sec. A combination of test machines and specimen geometries was investigated. Strain rates from 0--100\\/sec were generated using conventional and high speed hydraulic test machines. Strain rates from 10--1000\\/sec were generated using a

S. E. Groves; R. J. Sanchez; R. E. Lyon; A. E. Brown

1992-01-01

220

Electrode material comprising graphene-composite materials in a graphite network  

DOEpatents

A durable electrode material suitable for use in Li ion batteries is provided. The material is comprised of a continuous network of graphite regions integrated with, and in good electrical contact with a composite comprising graphene sheets and an electrically active material, such as silicon, wherein the electrically active material is dispersed between, and supported by, the graphene sheets.

Kung, Harold H.; Lee, Jung K.

2014-07-15

221

Paraffin\\/porous-graphite-matrix composite as a high and constant power thermal storage material  

Microsoft Academic Search

A new supported phase change material (PCM) made of paraffin impregnated by capillary forces in a compressed expansed natural graphite (CENG) matrix is presented. High loads of paraffin were obtained: from 65% to 95% weight depending upon the bulk graphite matrix density. Composite PCM\\/CENG thermal conductivities were found to be equivalent to those of the sole graphite matrix: from 4

Xavier Py; Régis Olives; Sylvain Mauran

2001-01-01

222

Method of tissue repair using a composite material  

DOEpatents

A composite biocompatible hydrogel material includes a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa. A calcium comprising salt is disposed in at least some of the pores. The porous polymer matrix can comprise cellulose, including bacterial cellulose. The composite can be used as a bone graft material. A method of tissue repair within the body of animals includes the steps of providing a composite biocompatible hydrogel material including a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa, and inserting the hydrogel material into cartilage or bone tissue of an animal, wherein the hydrogel material supports cell colonization in vitro for autologous cell seeding.

Hutchens, Stacy A; Woodward, Jonathan; Evans, Barbara R; O'Neill, Hugh M

2014-03-18

223

Bearing material. [composite material with low friction surface for rolling or sliding contact  

NASA Technical Reports Server (NTRS)

A composite material is described which will provide low friction surfaces for materials in rolling or sliding contact and is self-lubricating and oxidation resistant up to and in excess of about 930 C. The composite is comprised of a metal component which lends strength and elasticity to the structure, a fluoride salt component which provides lubrication and, lastly, a glass component which not only provides oxidation protection to the metal but may also enhance the lubrication qualities of the composite.

Sliney, H. E. (inventor)

1976-01-01

224

Preparation of Al8B4C7 composite materials by using oxide raw materials  

NASA Astrophysics Data System (ADS)

Al8B4C7 composites materials were prepared by using Al, B2O3 and C as raw materials. The effect of sintering temperature and different additives (Al and C) on Al8B4C7 composites materials were investigated. The Al8B4C7 composites materials were characterized from microstructure, apparent porosity, bulk density and compressive strength. The results demonstrated that the increasing of sintering temperatures could make the samples denser and improve compressive strength. The optimal sintering temperature was 1700 °C, and the main phase composition of Al8B4C7 composites materials were Al8B4C7 and Al2O3. Al additive could improve the properties while C additive played an harmful role. The Al8B4C7 grains were irregular flake and the size was 2~4 ?m.

Zhu, H. X.; Pan, C.; Deng, C. J.; Yuan, W. J.

2011-10-01

225

The development of composite materials for spacecraft precision reflector panels  

NASA Technical Reports Server (NTRS)

One of the critical technology needs for large precision reflectors required for future astrophysics and optical communications is in the area of structural materials. Therefore, a major area of the Precision Segmented Reflector Program at NASA is to develop lightweight composite reflector panels with durable, space environmentally stable materials which maintain both surface figure and required surface accuracy necessary for space telescope applications. Results from the materials research and development program at NASA Langley Research Center are discussed. Advanced materials that meet the reflector panel requirements are identified. Thermal, mechanical and durability properties of candidate materials after exposure to simulated space environments are compared to the baseline material.

Tompkins, Stephen S.; Bowles, David E.; Funk, Joan G.; Towell, Timothy W.; Lavoie, J. A.

1990-01-01

226

Composition and process for making an insulating refractory material  

DOEpatents

A composition and process for making an insulating refractory material. The composition includes calcined alumina powder, flash activated alumina powder, an organic polymeric binder and a liquid vehicle which is preferably water. Starch or modified starch may also be added. A preferred insulating refractory material made with the composition has a density of about 2.4-2.6 g/cm.sup.3 with reduced thermal conductivity, compared with tabular alumina. Of importance, the formulation has good abrasion resistance and crush strength during intermediate processing (commercial sintering) to attain full strength and refractoriness, good abrasion resistance and crush strength.

Pearson, Alan (Murrysville, PA); Swansiger, Thomas G. (Apollo, PA)

1998-04-28

227

Composition and process for making an insulating refractory material  

DOEpatents

A composition and process are disclosed for making an insulating refractory material. The composition includes calcined alumina powder, flash activated alumina powder, an organic polymeric binder and a liquid vehicle which is preferably water. Starch or modified starch may also be added. A preferred insulating refractory material made with the composition has a density of about 2.4--2.6 g/cm{sup 3} with reduced thermal conductivity, compared with tabular alumina. Of importance, the formulation has good abrasion resistance and crush strength during intermediate processing (commercial sintering) to attain full strength and refractoriness.

Pearson, A.; Swansiger, T.G.

1998-04-28

228

Method and apparatus for gripping uniaxial fibrous composite materials  

NASA Technical Reports Server (NTRS)

A strip specimen is cut from a unidirectional strong, brittle fiber composite material, and the surfaces of both ends of the specimen are grit blasted. The specimen is then placed between metal load transfer members having grit blasted surfaces. Sufficient compressive stress is applied to the load transfer members to prevent slippage during testing at both elevated temperatures and room temperatures. The need for adhesives, load pads, and other secondary composite processing is eliminated. This gripping system was successful in tensile testing, creep rupture testing, and fatigue testing uniaxial composite materials at 316 C.

Whittenberger, J. D.; Hurwitz, F. I. (inventors)

1984-01-01

229

Leaching of technologically enhanced naturally occurring radioactive materials.  

PubMed

A form of waste associated with mining activities is related to the type of deposit being mined and to the procedure of exploitation and enrichment adopted. The wastes usually contain relatively large amounts of technologically enhanced naturally occurring radioactive materials (TENORM). The TENORM are often stored on the surface. Consequently, they can be leached as a result of interaction with aqueous solutions of different chemical composition. This further leads to pollution of water and soil in the vicinity of the stored wastes. The paper presents the results of laboratory investigation aimed at quantifying the leaching process of samples originating from uranium dumps and storage reservoirs associated with brine pumped from coal mines. The leaching process was investigated with respect to selected elements: uranium isotopes, radium isotopes, iron, barium and sodium. The samples were exposed to aqueous solutions of different chemical composition. The experiments revealed that TENORM in form of sulphate compounds are the most resistant against leaching. The leaching coefficient for radium isotopes varies from a few thousandth percent to a few hundredth percent. On the other hand, for TENORM occurring in sand or sludge, the leaching coefficient for uranium and radium isotopes ranged from a few hundredth percent to a few percent. PMID:17482828

Chau, Nguyen Dinh; Chru?ciel, Edward

2007-08-01

230

ROLE OF FIBER MODIFICATION IN NATURAL FIBER COMPOSITE PROCESSING  

SciTech Connect

The prediction and characterization of the adhesion between fiber, surface treatment, and polymer is critical to the success of large-scale natural fiber based polymer composites in automotive semi-structural application. The two primary factors limiting the use of natural fiber in polymer composites are fiber moisture uptake and fiber degradation during high-temperature processing. In this study, we have developed several fiber surface modification techniques and analyzed the fiber-polymer adhesion of modified fibers to more clearly understand the critical parameters controlling moisture uptake, swelling, and fiber degradation due to interfacial structure. We will present a overview of surface modification techniques we have applied to date for hemp fiber sources, and illustrate a path to characterize surface modification effects on natural fiber adhesion in thermoplastic composites.

Fifield, Leonard S.; Denslow, Kayte M.; Gutowska, Anna; Simmons, Kevin L.; Holbery, Jim

2005-11-03

231

Composite resins. A review of the materials and clinical indications.  

PubMed

The aim of this work is to present the different components of the composites currently used in dentistry and furnish dentists with a basis that can provide criteria for choosing one or another to suit their therapeutic requirements. Most composites used in dentistry are hybrid materials, so-called because they are composed of polymer groups reinforced by an inorganic phase of glass fillers with different compositions, particle sizes and fill percentages. Flowable or condensable composites have attempted to provide an answer to certain functional requirements, although they have not been too successful at improving properties. Turning to polymerisation initiators, both halogen lamps, whether conventional or high intensity, and LED curing lights which provide a gradual increase in light intensity are very useful for reducing shrinkage of the composite material. The clinical choice of a composite must consider whether priority should be given to mechanical or aesthetic requirements: if mechanical considerations are paramount the material with the greatest volume of filler will be chosen; if aesthetic considerations predominate, particle size will be the most important factor. Additional components such as opaques and tints make it possible to improve the aesthetic results. Equally, the spread of other therapeutic procedures, such as tooth bleaching, has made it necessary to design composite materials in shades that are suitable for the special colour situations found in teeth treated by these methods. PMID:16505805

Hervás-García, Adela; Martínez-Lozano, Miguel Angel; Cabanes-Vila, Jose; Barjau-Escribano, Amaya; Fos-Galve, Pablo

2006-03-01

232

Electrospun Nanofiber Coating of Fiber Materials: A Composite Toughening Approach  

NASA Technical Reports Server (NTRS)

Textile-based composites could significantly benefit from local toughening using nanofiber coatings. Nanofibers, thermoplastic or otherwise, can be applied to the surface of the fiber tow bundle, achieving toughening of the fiber tow contact surfaces, resulting in tougher and more damage-resistant/tolerant composite structures. The same technique could also be applied to other technologies such as tape laying, fiber placement, or filament winding operations. Other modifications to the composite properties such as thermal and electrical conductivity could be made through selection of appropriate nanofiber material. Control of the needle electric potential, precursor solution, ambient temperature, ambient humidity, airflow, etc., are used to vary the diameter and nanofiber coating morphology as needed. This method produces a product with a toughening agent applied to the fiber tow or other continuous composite precursor material where it is needed (at interfaces and boundaries) without interfering with other composite processing characteristics.

Kohlman, Lee W.; Roberts, Gary D.

2012-01-01

233

Functional composite materials based on chemically converted graphene.  

PubMed

Graphene, a one-atom layer of graphite, possesses a unique two-dimensional structure and excellent mechanical, thermal, and electrical properties. Thus, it has been regarded as an important component for making various functional composite materials. Graphene can be prepared through physical, chemical and electrochemical approaches. Among them, chemical methods were tested to be effective for producing chemically converted graphene (CCG) from various precursors (such as graphite, carbon nanotubes, and polymers) in large scale and at low costs. Therefore, CCG is more suitable for synthesizing high-performance graphene based composites. In this progress report, we review the recent advancements in the studies of the composites of CCG and small molecules, polymers, inorganic nanoparticles or other carbon nanomaterials. The methodology for preparing CCG and its composites has been summarized. The applications of CCG-based functional composite materials are also discussed. PMID:21360763

Bai, Hua; Li, Chun; Shi, Gaoquan

2011-03-01

234

Light weight polymer matrix composite material  

NASA Technical Reports Server (NTRS)

A graphite fiber reinforced polymer matrix is layed up, cured, and thermally aged at about 750.degree. F. in the presence of an inert gas. The heat treatment improves the structural integrity and alters the electrical conductivity of the materials. In the preferred embodiment PMR-15 polyimides and Celion-6000 graphite fibers are used.

Bowles, Kenneth J. (Inventor); Lowell, Carl E. (Inventor)

1991-01-01

235

Investigating Tungsten Concentrations and Isotopic Compositions of Natural Water Samples from the Carson River Basin  

NASA Astrophysics Data System (ADS)

Recent studies have shown that W-isotopes may fractionate in nature1; however, the magnitude and cause of the isotopic variations are largely unknown and unconstrained. In this study, the isotopic compositions of the NIST 3163 W standard, W ore minerals, and 15 natural surface waters from Nevada's Carson River Basin were analyzed by MC-ICP-MS using external bracketing with NIST 3163 and the IUPAC 184W/183W for mass bias correction. Chemical separation procedures were developed to purify W from natural matrices and tested to assure fractionation was not introduced during column chemistry. The W isotopic compositions of these samples were measured and compared to the accepted IUPAC composition of natural W. Samples of wolframite (Fe, MnWO4) and hubnerite (MnWO4) have compositions similar to the IUPAC value but vary from the isotopic composition of NIST 3163 - particularly in 182W/183W. The isotopic compositions of the natural waters, except for an extremely evaporated sample from Soda Lake, are similar to the NIST standard. This evaporative lake, formed by a maar, has a unique chemical composition compared to other surface waters with high W (800 ± 20 ng/g) and As (1665 ± 17 ng/g) concentrations; and relatively low Fe (5.00 ± 0.13 ng/g) and Mn (0.52 ± 0.07 ng/g). These results support recent observations of natural W isotopic variation and imply that W-isotope compositions may be useful for environmental applications of stable isotope geochemistry. 1. Irisawa, K. and Hirata, T. (2006) Tungsten isotopic analysis on six geochemical reference materials using multiple collector-ICP-mass spectrometry coupled with a rhenium-external correction technique. Journal of Analytical Atomic Spectrometry 21, 1387-1395.

Wasserman, N. L.; Williams, R. W.; Kayzar, T. M.; Schorzman, K. C.

2012-12-01

236

3D Magnetic Reluctivity Tensor of Soft Magnetic Composite Material  

Microsoft Academic Search

Soft magnetic composite (SMC) materials are particularly suitable for construction of electrical machines with complex structure and 3D magnetic flux. For design and analysis of such 3D flux machines, 3D magnetic properties of the magnetic materials should be properly determined, modeled and applied for calculating the magnetic field distribution, parameters and performance. This paper presents the 3D magnetic property measurement

Y. G. Guo; J. G. Zhu; Z. W. Lin; J. J. Zhong; H. Y. Lu; S. H. Wang

2006-01-01

237

Composite Material Property Nondestructive Characterization Using Obliquely Insonified Ultrasonic Waves  

NASA Technical Reports Server (NTRS)

The analysis of reflected ultrasonic waves induced by oblique insonification of composite materials is a powerful tool for providing informations about defects and material properties. A device was developed to manipulate a pair of transmitting and receiving transducers at vrious angles of wave incidence and propagation with the fiber orientation.

Bar-Cohen, Y.; Mal, A. K.; Lih, S.

1994-01-01

238

Properties of graphite composites based on natural and synthetic graphite powders and a phenolic novolac binder  

NASA Astrophysics Data System (ADS)

Model graphite composites, similar to those used in nuclear applications as encasement material in fuel pebbles, were prepared by uniaxial cold compression moulding. They contained natural flake graphite, synthetic graphite and 20 wt.% phenolic novolac resin binder. The materials were carbonised at 900 °C in a nitrogen atmosphere and then annealed at 1800 °C in helium atmosphere. The X-ray diffraction studies showed that the graphite in these composites had hexagonal crystal structure after annealing. Raman spectroscopy revealed the presence of the structurally disordered phase derived from the carbonised resin. Optical microscopy revealed a flake-like microstructure for composites containing mainly natural graphite and needle-coke like particles for composites containing mainly synthetic graphite. The composites featured anisotropic property behaviour as the particles were partially aligned in a direction perpendicular to the compression direction. Thermogravimetric analysis studies showed that the annealed graphite composites were stable in air to 650 °C. The linear thermal expansion coefficients measured by thermomechanical analysis (20-600 °C) in the direction of pressing were in the range 5-9 × 10-6 K-1 and in the range 1.2-2 × 10-6 K-1 in the direction normal to pressing. The thermal conductivity of the composites were measured using Xenon flash method from 100 to 1000 °C and the values ranged from 19 to 30 W m-1 K-1.

Magampa, P. P.; Manyala, N.; Focke, W. W.

2013-05-01

239

Polymeric compositions incorporating polyethylene glycol as a phase change material  

DOEpatents

A polymeric composition comprising a polymeric material and polyethylene glycol or end-capped polyethylene glycol as a phase change material, said polyethylene glycol and said end-capped polyethylene glycol having a molecular weight greater than about 400 and a heat of fusion greater than about 30 cal/g; the composition is useful in making molded and/or coated materials such as flooring, tiles, wall panels and the like; paints containing polyethylene glycols or end-capped polyethylene glycols are also disclosed.

Salyer, Ival O. (Dayton, OH); Griffen, Charles W. (Mason, OH)

1989-01-01

240

DOE Automotive Composite Materials Research: Present and Future Efforts  

SciTech Connect

One method of increasing automotive energy efficiency is through mass reduction of structural components by the incorporation of composite materials. Significant use of glass reinforced polymers as structural components could yield a 20--30% reduction in vehicle weight while the use of carbon fiber reinforced materials could yield a 40--60% reduction in mass. Specific areas of research for lightweighting automotive components are listed, along with research needs for each of these categories: (1) low mass metals; (2) polymer composites; and (3) ceramic materials.

Warren, C.D.

1999-08-10

241

Workshop on Scaling Effects in Composite Materials and Structures  

NASA Technical Reports Server (NTRS)

This document contains presentations and abstracts from the Workshop on Scaling Effects in Composite Materials and Structures jointly sponsored by NASA Langley Research Center, Virginia Tech, and the Institute for Mechanics and Materials at the University of California, San Diego, and held at NASA Langley on November 15-16, 1993. Workshop attendees represented NASA, other government research labs, the aircraft/rotorcraft industry, and academia. The workshop objectives were to assess the state-of-technology in scaling effects in composite materials and to provide guidelines for future research.

Jackson, Karen E. (compiler)

1994-01-01

242

Materials Science and Technology Teacher's Handbook: Experiments/Demonstrations: Composites  

NSDL National Science Digital Library

This chapter from the Materials Science and Technology Teacher's Handbook provides experiments and demonstrations involving composites that can be used in a materials science and technology curriculum. These experiments are "designed to grab studentsâ attention, pull their minds from predictable everyday classroom activities, give them something to look forward to, and teach them some simple principles and properties used by materials scientists." Experiments include Making Concrete, Simple Stressed-Skin Composite, Airfoils, and Making Paper. Drawings and diagrams help illustrate the concepts. This document will serve as a framework for instructors and may be downloaded in PDF format.

2012-10-05

243

Acoustic emission from composite materials. [nondestructive tests  

NASA Technical Reports Server (NTRS)

The two basic areas where the acoustic emission (AE) technique can be applied are materials research and the evaluation of structural reliability. This experimental method leads to a better understanding of fracture mechanisms and is an NDT technique particularly well suited for the study of propagating cracks. Experiments are described in which acoustic emissions were unambiguously correlated with microstructural fracture mechanisms. The advantages and limitations of the AE technique are noted.

Visconti, I. C.; Teti, R.

1979-01-01

244

Probing disease-related proteins with fluorogenic composite materials.  

PubMed

Construction of composite materials based on the self-assembly of fluorescently labeled biomolecules with a variety of micro- or nano-quenching materials (by the Förster Resonance Energy Transfer mechanism) for the fluorogenic recognition of disease-related proteins has become a dynamic research topic in the field of fluorescence recognition. Here we summarize the recent progress on the composition of fluorescence dye-labeled biomolecules including sugars, peptides and nucleotides with organic (graphene and carbon nanotubes) and inorganic (gold nanoparticles) materials. Their application in the fluorescence detection of proteins and enzymes on both the molecular and cellular levels is discussed. Perspectives are proposed with respect to the future directions of employing these composite materials in the recognition of pathological proteins. PMID:25474366

He, Xiao-Peng; Zang, Yi; James, Tony D; Li, Jia; Chen, Guo-Rong

2014-12-01

245

Heavily loaded ferrite-polymer composites to produce high refractive index materials at centimetre wavelengths  

NASA Astrophysics Data System (ADS)

A cold-pressing technique has been developed for fabricating composites composed of a polytetrafluoroethylene-polymer matrix and a wide range of volume-fractions of MnZn-ferrite filler (0%-80%). The electromagnetic properties at centimetre wavelengths of all prepared composites exhibited good reproducibility, with the most heavily loaded composites possessing simultaneously high permittivity (180 ± 10) and permeability (23 ± 2). The natural logarithm of both the relative complex permittivity and permeability shows an approximately linear dependence with the volume fraction of ferrite. Thus, this simple method allows for the manufacture of bespoke materials required in the design and construction of devices based on the principles of transformation optics.

Parke, L.; Hooper, I. R.; Hicken, R. J.; Dancer, C. E. J.; Grant, P. S.; Youngs, I. J.; Sambles, J. R.; Hibbins, A. P.

2013-10-01

246

A grammatical approach to customization of shape and composite materials  

NASA Astrophysics Data System (ADS)

With the increasing use of composite materials in Mechanical and Aerospace industries, an approach is required to facilitate designing of components using composite materials, while ensuring customization of the shape such a way that multiple design goals for the components are satisfied. Existing design methods may be used in some cases, where the component shape and loadings are simple. While a significant amount of research has been conducted to study the properties of composite materials, little attention has been paid to find out a design approach such that (1) the user requirements in the very general form may be used directly and as the input for the design, (2) the best possible composite material are selected to meet multiple desired functions, and (3) shape variation is analyzed in order to enable mass customization of the design. Thus an approach is required that will be able to handle both the shape and the material in order to design a load bearing component using composite materials. In this research the focus is to develop a design approach that will consider the user requirements for a composite component in its very general form and generate component shape and material details in a systematic order so that the designed component can withstand a given loading condition. Consequently, the Primary Research Question is: How to simultaneously explore shape and composite materials during the design of a product to meet multiple property and functional goals? The wide range of properties, covered by various fiber-matrix combinations, along with their directional property characteristics, maximizes the flexibility of the designers, while designing composite material products. Meeting multiple property goals, however, complicates the design process as both the composite material selection and the component shape formation becomes highly intricate with the loading conditions and a number of matrix calculations needs to be performed to determine theoretical value of composite material properties. A grammar is a formal definition of a language written in transformational form. To address these issues, in this research a grammatical approach is developed that will generate a shape grammar to perform shape optimization, and then incorporate a composite material selection system and loading analysis techniques of Solid Mechanics in order to design load bearing components of irregular shape. The approach will be able to consider the user requirements in the very general text form, convert them to the design requirements for the component, generate optimized shape based on multiple design constraints, perform the complete design work, and generate the component. The major contributions include: (1) generating a shape grammar to represent functions of the load bearing component such a way that mass-customization of shape is possible, (2) developing a composite material customization system in order to satisfy directional property requirements, and (3) introducing a unique laminate design approach in order to satisfy design property requirements at the critical cross-sections locally that can result in highly efficient design compared to conventional design method. Verification of the approach will focus on its application to simultaneously explore shapes and customization of composite materials.

Nandi, Soumitra

247

Measurement of Damping of Composite Materials for Turbomachinery Applications  

NASA Technical Reports Server (NTRS)

The scientific community has felt that ceramic matrix composite (CMC) materials possess more material damping than the superalloys used in the production of rocket engine turbomachinery turbine-end components. The purpose of this NASA/MFSC study is to quantify the damping in CMC's as compared to a typical super-alloy, Inconel 718. It was observed through testing of beam coupons and disk specimens that the CMC's do indeed possess more material damping than the baselined alloy Inconel 718.

Harris, D. L.

1998-01-01

248

The role of polymer based composites materials in modern and future aerospace structures  

NASA Astrophysics Data System (ADS)

The need to reduce the overall weight of aeronautical and space structures, while at the same time preserving or even improving their performances, make the research and development in the field of innovative structures and advanced composite materials a crucial step for the advancement of aerospace technologies. Several fields of innovation have been explored in the last decades but the most promising solutions for the future of aerospace structures will be found in the "intelligent" use of polymer based composite materials both in the design and in their "nature like" use.

Cantoni, Stefania; De Nicola, Felice; Mercurio, Umberto; Quaranta, Vincenzo

2014-05-01

249

Molecular interactions in inorganic-organic composite materials  

NASA Astrophysics Data System (ADS)

Inorganic-organic interactions play a key role in determining the molecular and macroscopic properties of resulting composites. These materials have a wide variety of applications including use as catalysts, hosts for optical and electronic applications, and as adsorbents. Tailoring composites for each unique application is accomplished using local interactions between inorganic and organic species to control both local and mesoscopic ordering. For many inorganic-organic composites, no local order exists thereby inhibiting local characterization of these materials using diffraction techniques. However, using NMR methods that are not dependent upon periodicity, unique insight about inorganic-organic interactions in locally amorphous materials can be achieved. Using solid-state NMR methods, inorganic-organic interactions have been utilized to unambiguously establish the local organization of a variety of mesoporous materials as well as provide insight into the biological processes controlling biomineralization. For example, such experiments have revealed the location and coordination of aluminum species in the aluminosilicate framework of mesoporous materials. Such findings are crucial for the preparation of advanced catalytically active materials. These techniques have also provided increase understanding of the formation process of the inorganic network and have lead to the synthesis of the first mesophase material with a 2D crystalline architecture. This discovery is promising for enhancing the thermal and mechanical strength of mesoporous catalysts that had previously been locally disordered and thermally unstable. These investigations provide a wealth of knowledge for understanding the influence organic molecules exert upon silica structures and can be utilized to provide advanced, tailored composites.

Christiansen, Sean Condon

250

Review on advanced composite materials boring mechanism and tools  

NASA Astrophysics Data System (ADS)

With the rapid development of aviation and aerospace manufacturing technology, advanced composite materials represented by carbon fibre reinforced plastics (CFRP) and super hybrid composites (fibre/metal plates) are more and more widely applied. The fibres are mainly carbon fibre, boron fibre, Aramid fiber and Sic fibre. The matrixes are resin matrix, metal matrix and ceramic matrix. Advanced composite materials have higher specific strength and higher specific modulus than glass fibre reinforced resin composites of the 1st generation. They are widely used in aviation and aerospace industry due to their high specific strength, high specific modulus, excellent ductility, anticorrosion, heat-insulation, sound-insulation, shock absorption and high&low temperature resistance. They are used for radomes, inlets, airfoils(fuel tank included), flap, aileron, vertical tail, horizontal tail, air brake, skin, baseboards and tails, etc. Its hardness is up to 62~65HRC. The holes are greatly affected by the fibre laminates direction of carbon fibre reinforced composite material due to its anisotropy when drilling in unidirectional laminates. There are burrs, splits at the exit because of stress concentration. Besides there is delamination and the hole is prone to be smaller. Burrs are caused by poor sharpness of cutting edge, delamination, tearing, splitting are caused by the great stress caused by high thrust force. Poorer sharpness of cutting edge leads to lower cutting performance and higher drilling force at the same time. The present research focuses on the interrelation between rotation speed, feed, drill's geometry, drill life, cutting mode, tools material etc. and thrust force. At the same time, holes quantity and holes making difficulty of composites have also increased. It requires high performance drills which won't bring out defects and have long tool life. It has become a trend to develop super hard material tools and tools with special geometry for drilling composite materials.

Shi, Runping; Wang, Chengyong

2010-12-01

251

Review on advanced composite materials boring mechanism and tools  

NASA Astrophysics Data System (ADS)

With the rapid development of aviation and aerospace manufacturing technology, advanced composite materials represented by carbon fibre reinforced plastics (CFRP) and super hybrid composites (fibre/metal plates) are more and more widely applied. The fibres are mainly carbon fibre, boron fibre, Aramid fiber and Sic fibre. The matrixes are resin matrix, metal matrix and ceramic matrix. Advanced composite materials have higher specific strength and higher specific modulus than glass fibre reinforced resin composites of the 1st generation. They are widely used in aviation and aerospace industry due to their high specific strength, high specific modulus, excellent ductility, anticorrosion, heat-insulation, sound-insulation, shock absorption and high&low temperature resistance. They are used for radomes, inlets, airfoils(fuel tank included), flap, aileron, vertical tail, horizontal tail, air brake, skin, baseboards and tails, etc. Its hardness is up to 62~65HRC. The holes are greatly affected by the fibre laminates direction of carbon fibre reinforced composite material due to its anisotropy when drilling in unidirectional laminates. There are burrs, splits at the exit because of stress concentration. Besides there is delamination and the hole is prone to be smaller. Burrs are caused by poor sharpness of cutting edge, delamination, tearing, splitting are caused by the great stress caused by high thrust force. Poorer sharpness of cutting edge leads to lower cutting performance and higher drilling force at the same time. The present research focuses on the interrelation between rotation speed, feed, drill's geometry, drill life, cutting mode, tools material etc. and thrust force. At the same time, holes quantity and holes making difficulty of composites have also increased. It requires high performance drills which won't bring out defects and have long tool life. It has become a trend to develop super hard material tools and tools with special geometry for drilling composite materials.

Shi, Runping; Wang, Chengyong

2011-05-01

252

Cytotoxicity of composite materials polymerized with LED curing units.  

PubMed

The proper intensity and illumination time of a curing light is of great importance for the complete polymerization of resin composites and long-lasting resin composite restorations. Inadequately cured resin composites can have a cytotoxic effect on pulp tissue by releasing unreacted monomers. This study determined whether there is any difference in cytotoxicity between composite materials illuminated with different curing modes of LED curing units. Thin layers of two composite materials were polymerized using three different modes of the Bluephase C8 LED curing unit: a high intensity mode (HIP-800 mW/cm2, 20 seconds), a soft-start mode (SOF-650 mW/cm2 first 5 seconds, 800 mW/cm2 next 25 seconds) and a low intensity mode (LOP-650 mW/cm2, 30 seconds). Lymphocyte cultures were treated with both polymerized and unpolymerized composites using one of the modes stated above. Cells were analyzed using the trypan blue exclusion test, the acridine orange/ethidium bromide dying technique and an alkaline comet assay. Significant cytotoxicity was observed for 120 mg of unpolymerized composites and those polymerized with the HIP polymerization mode. A significant level of DNA damage was detected for 120 mg of unpolymerized composites. However, curing via the LOP program exhibited the lowest genotoxicity. Longer curing time with lower intensity results in less cytotoxicity than shorter curing exposure using a higher intensity of light emitted from the curing light source. PMID:18335729

Knezevic, Alena; Zeljezic, Davor; Kopjar, Nevenka; Tarle, Zrinka

2008-01-01

253

Development of chemical vapor composites, CVC materials. Final report  

SciTech Connect

Industry has a critical need for high-temperature operable ceramic composites that are strong, non-brittle, light weight, and corrosion resistant. Improvements in energy efficiency, reduced emissions and increased productivity can be achieved in many industrial processes with ceramic composites if the reaction temperature and pressure are increased. Ceramic composites offer the potential to meet these material requirements in a variety of industrial applications. However, their use is often restricted by high cost. The Chemical Vapor composite, CVC, process can reduce the high costs and multiple fabrication steps presently required for ceramic fabrication. CVC deposition has the potential to eliminate many difficult processing problems and greatly increase fabrication rates for composites. With CVC, the manufacturing process can control the composites` density, microstructure and composition during growth. The CVC process: can grow or deposit material 100 times faster than conventional techniques; does not require an expensive woven preform to infiltrate; can use high modulus fibers that cannot be woven into a preform; can deposit composites to tolerances of less than 0.025 mm on one surface without further machining.

NONE

1998-10-05

254

Mesoporous MFI zeolite material from silica–alumina\\/epoxy-resin composite material and its catalytic activity  

Microsoft Academic Search

Although the versatilities of zeolitic materials are widely known to chemists and materials scientists, their exclusive microporosity sometimes causes various defections especially in the diffusion of reactant and product molecules in catalytic reactions. Silica–alumina\\/epoxy-resin composite materials were obtained from TMOS (tetramethoxysilane), aluminum acetylacetonate and bisphenol A diglycidyl ether with a cyclic acid anhydride as both condensation and curing reagents. Hydrothermal

Masahiro Fujiwara; Akinori Sakamoto; Kumi Shiokawa; Astam K. Patra; Asim Bhaumik

2011-01-01

255

Fabrication of Composite Material Using Gettou Fiber by Injection Molding  

NASA Astrophysics Data System (ADS)

This study investigated the mechanical properties of composite using gettou (shell ginger) fiber as reinforcement fabricated from injection molding. Gettou fiber is a natural fiber made from gettou, a subtropical plant that is largely abundant in Okinawa, Japan. We used the stem part of gettou plant and made the gettou fiber by crushing the stem. The composite using gettou fiber contributed to low shrinkage ratio, high bending strength and high flexural modulus. The mechanical strength of composite using long gettou fiber showed higher value than composite using short gettou fiber. Next, because gettou is particularly known for its anti-mold characteristic, we investigated the characteristic in gettou plastic composite. The composite was tested against two molds: aspergillius niger and penicillium funiculosum. The 60% gettou fiber plastic composite was found to satisfy the JISZ2801 criterion. Finally, in order to predict the flexural modulus of composite using gettou fiber by Halpin-Tsai equation, the tensile elastic modulus of single gettou fiber was measured. The tendency of the experimental results of composite using gettou fiber was in good agreement with Halpin-Tsai equation.

Setsuda, Roy; Fukumoto, Isao; Kanda, Yasuyuki

256

A new technique for simulating composite material  

NASA Technical Reports Server (NTRS)

This project dealt with the development on new methodologies and algorithms for the multi-spectrum electromagnetic characterization of large scale nonmetallic airborne vehicles and structures. A robust, low memory, and accurate methodology was developed which is particularly suited for modern machine architectures. This is a hybrid finite element method that combines two well known numerical solution approaches. That of the finite element method for modeling volumes and the boundary integral method which yields exact boundary conditions for terminating the finite element mesh. In addition, a variety of high frequency results were generated (such as diffraction coefficients for impedance surfaces and material layers) and a class of boundary conditions were developed which hold promise for more efficient simulations. During the course of this project, nearly 25 detailed research reports were generated along with an equal number of journal papers. The reports, papers, and journal articles are listed in the appendices along with their abstracts.

Volakis, John L.

1991-01-01

257

A new ferromagnetic hysteresis model for soft magnetic composite materials  

NASA Astrophysics Data System (ADS)

A new ferromagnetic hysteresis model for soft magnetic composite materials based on their specific properties is presented. The model relies on definition of new anhysteretic magnetization based on the Cauchy-Lorentz distribution describing the maximum energy state of magnetic moments in material. Specific properties of soft magnetic composite materials (SMC) such as the presence of the bonding material, different sizes and shapes of the Fe particles, level of homogeneity of the Fe particles at the end of the SMC product treatment, and achieved overall material density during compression, are incorporated in both the anhysteretic differential magnetization susceptibility and the irreversible differential magnetization susceptibility. Together they form the total differential magnetization susceptibility that defines the new ferromagnetic hysteresis model. Genetic algorithms are used to determine the optimal values of the proposed model parameters. The simulated results show good agreement with the measured results.

Zidari?, Bogomir; Miljavec, Damijan

2011-01-01

258

Improved Composites Using Crosslinked, Surface-Modified Carbon Nanotube Materials  

NASA Technical Reports Server (NTRS)

Individual carbon nanotubes (CNTs) exhibit exceptional tensile strength and stiffness; however, these properties have not translated well to the macroscopic scale. Premature failure of bulk CNT materials under tensile loading occurs due to the relatively weak frictional forces between adjacent CNTs, leading to poor load transfer through the material. When used in polymer matrix composites (PMCs), the weak nanotube-matrix interaction leads to the CNTs providing less than optimal reinforcement.Our group is examining the use of covalent crosslinking and surface modification as a means to improve the tensile properties of PMCs containing carbon nanotubes. Sheet material comprised of unaligned multi-walled carbon nanotubes (MWCNT) was used as a drop-in replacement for carbon fiber in the composites. A variety of post-processing methods have been examined for covalently crosslinking the CNTs to overcome the weak inter-nanotube shear interactions, resulting in improved tensile strength and modulus for the bulk sheet material. Residual functional groups from the crosslinking chemistry may have the added benefit of improving the nanotube-matrix interaction. Composites prepared using these crosslinked, surface-modified nanotube sheet materials exhibit superior tensile properties to composites using the as received CNT sheet material.

Baker, James Stewart

2014-01-01

259

Simulation of composite material response under dynamic compressive loading  

SciTech Connect

Realistic computer prediction of high-velocity impact and penetration events involving composite materials requires a knowledge of the material behavior under large compressive stresses at high rates of deformation. As an aid to the development of constitutive models for composites under these conditions, methods for numerical simulation of the material response at the microstructural level are being developed. At present, the study is confined to glass fiber/epoxy composites. The technique uses a numerical model of a representative sample of the microstructure with randomly distributed fibers. By subjecting the boundary of this numerical sample to prescribed loading histories, a statistical interpretation allows prediction of the global material response. Because the events at the microstructural scale involve locally large deformation, and because of the constantly changing picture with regard to contact between the fibers, the Eulerian code CTH is used for these calculations. Certain aspects of material failure can also be investigated using this approach. The method allows the mechanical behavior of composite materials to be studied with fewer assumptions about constituent behavior and morphology than typically required in analytical efforts.

Silling, S.A.; Taylor, P.A.

1993-12-31

260

ADSORPTION OF ORGANIC CATIONS TO NATURAL MATERIALS  

EPA Science Inventory

The factors that control the extent of adsorption of amphiphilic organic cations on environmental and pristine surfaces have been studied. The sorbents were kaolinite, montmorillonite, two aquifer materials, and a soil; solutions contained various concentrations of NaCl and CaCl,...

261

ADSORPTION OF ORGANIC CATIONS TO NATURAL MATERIALS  

EPA Science Inventory

The factors that control the extent of adsorption of amphiphilic organic cations on environmental and pristine surfaces have been studied. he sorbents were kaolinite, montmorillonite, two aquifer materials, and a soil; solutions contained various concentrations of NaCl and CaC12,...

262

Experimental Investigation of Textile Composite Materials Using Moire Interferometry  

NASA Technical Reports Server (NTRS)

The viability as an efficient aircraft material of advanced textile composites is currently being addressed in the NASA Advanced Composites Technology (ACT) Program. One of the expected milestones of the program is to develop standard test methods for these complex material systems. Current test methods for laminated composites may not be optimum for textile composites, since the architecture of the textile induces nonuniform deformation characteristics on the scale of the smallest repeating unit of the architecture. The smallest repeating unit, also called the unit cell, is often larger than the strain gages used for testing of tape composites. As a result, extending laminated composite test practices to textiles can often lead to pronounced scatter in material property measurements. It has been speculated that the fiber architectures produce significant surface strain nonuniformities, however, the magnitudes were not well understood. Moire interferometry, characterized by full-field information, high displacement sensitivity, and high spatial resolution, is well suited to document the surface strain on textile composites. Studies at the NASA Langley Research Center on a variety of textile architectures including 2-D braids and 3-D weaves, has evidenced the merits of using moire interferometry to guide in test method development for textile composites. Moire was used to support tensile testing by validating instrumentation practices and documenting damage mechanisms. It was used to validate shear test methods by mapping the full-field deformation of shear specimens. Moire was used to validate open hole tension experiments to determine the strain concentration and compare then to numeric predictions. It was used for through-the-thickness tensile strength test method development, to verify capabilities for testing of both 2-D and 3-D material systems. For all of these examples, moire interferometry provided vision so that test methods could be developed with less speculation and more documentation.

Ifju, Peter G.

1995-01-01

263

The effective Kerr constant of an electrooptical composite material  

Microsoft Academic Search

A general relationship is derived for the effective Kerr constant of an electrooptical composite material containing nonlinear\\u000a centrosymmetric dielectric microcrystals; anisotropy of the inclusions and their nonsphericity were taken into account. It\\u000a is shown that nonsphericity of the particles makes it possible to substantially enhance the Kerr constant of the composite\\u000a in the case when the glass-matrix permittivity is much

A. A. Berezhno?; M. I. Vasil’ev; A. O. Volchek; A. V. Dotsenko; V. A. Tsekhomskii

2002-01-01

264

Pin bearing evaluation of LTM25 composite materials  

NASA Technical Reports Server (NTRS)

This report summarizes pin bearing evaluations of LTM25 composite materials. Northrop Grumman Corporation conducted pin bearing testing and fabricate two panels from composite materials that cure at low temperatures. These materials are being incorporated into Unmanned Aerial Vehicles (UAVS) to reduce manufacturing costs since they allow the use of low-cost tooling and facilities. Two composite prepreg product forms were evaluated; MR50/LTM25 unidirectional tape, batch 2881vd and CFS003/LTM25 woven cloth, batch 2216. Northrop Grumman fabricated, machined, and tested specimens to determine the bearing strength in accordance with MIL-HDBK-17D, Volume 1, Section 7.2.4. Quasi-isotropic laminates from the two product forms were fabricated for these tests. In addition, 2 quasi-isotropic panels of dimensions 12 in. x 28 in. were fabricated (one each from the two product forms), inspected, and shipped to NASA Langley for further evaluation.

Shah, C. H.; Postyn, A. S.

1996-01-01

265

Antibacterial activity of resin composites with silver-containing materials.  

PubMed

Resin composites with antibacterial activity may be useful to decrease the frequency of secondary caries around restorations. The purposes of this study were to investigate the antibacterial activity of light-activated resin composites incorporating one of three silver-containing materials and to evaluate their long-term inhibitory effect against Streptococcus mutans The three types of silver-containing materials, Novaron (N), Amenitop (AM), and AIS, were incorporated into TEGDMA-UDMA-based light-activated resin composites, and the antibacterial activities, mechanical properties and release of silver ions were examined. Minimum inhibitory concentrations in suspensions of N, AM, and AIS against S. mutans were 1.1, 1.2, and 23.0 mg/ml, respectively. Resin composites incorporating 5 wt% of Novaron (N-5) and 7 wt% of Amenitop (AM-7) inhibited the growth of S. mutans after immersion in water for 3 months, whereas the resin composite incorporating 10 wt% of AIS did not. No significant difference in either compressive or flexural strength was observed between the control and N-5 composites after 1 d and 3 months storage in water. However, for AM-5 composite, there was a significant difference in both strength parameters between the two immersion periods. There was no or extremely little release of silver ions from the N-5 and AM-5 composites after 1 d or 3 months immersion in water. These results indicated that a light-activated resin composite incorporating silver-containing materials such as Novaron may be clinically useful due to its long-term inhibitory effect against S. mutans and favorable mechanical properties. PMID:10467945

Yoshida, K; Tanagawa, M; Matsumoto, S; Yamada, T; Atsuta, M

1999-08-01

266

Structure and Physical Properties of Natural Gellous Materials  

NASA Astrophysics Data System (ADS)

This study presents two types of natural gellous materials as cellulose resources including gellous material synthesized by Acetobacter xylinum in fermentation process of coconut water with common name Bacterial Cellulose (BC) and gellous material isolated from seed of Ocimum americanum called hydrogel. Morphological surface of BC and hydrogel was observed by Scanning Electron Microscope (SEM). These images show randomly arrangement of fibres in three dimensional network having length of 1-5 µm and 3-12µm, respectively in forming a dense reticulated structure. Hydrated fibres were observed evidently by Atomic Force Microscope (AFM) showing that BC and hydrogel have fibres in nanometer scale diameter, 7-10 and 2-3 nm, respectively. At glance, X-Ray diffraction profile of hydrogel shows broadening peaks at 2?, 16° and 22°. While BC has peaks at 2?, 14.7, 16.7, 20.5 and 22.5°, attributed to lattice diffractions (100), (010), and (110), respectively. The sharp profile present in BC lead to ordered structure, confirmed by higher crystallinity degree of BC (75%) compared to that`s of hydrogel (35%). Water Holding Capacity (WHC) of BC and hydrogel has values about 5.5 and 39.2 mL g-1, respectively while swelling ability of BC and hydrogel in water is 6.2 and 102.2%, respectively. Neutral sugar compositions of BC resulted in less 0.1% arabinose and rhamnose, 1.1% galactose, 98.5% glucose, 0.2 xylose and 0.2 mannose indicating high cellulose content. Meanwhile, hydrogel contains 11.9% (arabinose), 4.5% (rhamnose), 18.6% (galactose), 50.5% (glucose), 13.2% (xylose), 1.3% (mannose) indicating high hemicellulose contents leading to branching of arabinogalactan attached to cellulose.

Yudianti, Rike; Indrarti, Lucia; Azuma, Jun-Ichi

267

Holographic imaging of natural-fiber-containing materials  

DOEpatents

The present invention includes methods and apparatuses for imaging material properties in natural-fiber-containing materials. In particular, the images can provide quantified measures of localized moisture content. Embodiments of the invention utilize an array of antennas and at least one transceiver to collect amplitude and phase data from radiation interacting with the natural-fiber-containing materials. The antennas and the transceivers are configured to transmit and receive electromagnetic radiation at one or more frequencies, which are between 50 MHz and 1 THz. A conveyance system passes the natural-fiber-containing materials through a field of view of the array of antennas. A computing device is configured to apply a synthetic imaging algorithm to construct a three-dimensional image of the natural-fiber-containing materials that provides a quantified measure of localized moisture content. The image and the quantified measure are both based on the amplitude data, the phase data, or both.

Bunch, Kyle J [Richland, WA; Tucker, Brian J [Pasco, WA; Severtsen, Ronald H [Richland, WA; Hall, Thomas E [Kennewick, WA; McMakin, Douglas L [Richland, WA; Lechelt, Wayne M [West Richland, WA; Griffin, Jeffrey W [Kennewick, WA; Sheen, David M [Richland, WA

2010-12-21

268

Effective thermal conductivity of a thin composite material  

SciTech Connect

The thermal conductivity of a randomly oriented composite material is modeled using a probabilistic approach in order to determine if a size effect exists for the thermal conductivity at small composite thickness. The numerical scheme employs a random number generator to position the filler elements, which have a relatively high thermal conductivity, within a matrix having a relatively low thermal conductivity. Results indicate that, below some threshold thickness, the composite thermal conductivity increases with decreasing thickness, while above the threshold the thermal conductivity is independent of thickness. The threshold thickness increases for increasing filler fraction and increasing k{sub f}/k{sub m}, the ratio between filler and matrix thermal conductivities.

Phelan, P.E. [Arizona State Univ., Tempe, AZ (United States). Dept. of Mechanical and Aerospace Engineering; Niemann, R.C. [Argonne National Lab., IL (United States)

1996-12-31

269

Electrostatic Discharge Sensitivity and Electrical Conductivity of Composite Energetic Materials  

SciTech Connect

Composite energetic material response to electrical stimuli was investigated and a correlation between electrical conductivity and ignition sensitivity was examined. The composites consisted of micrometer particle aluminum combined with another metal, metal oxide, or fluoropolymer. Of the nine tested mixtures, aluminum with copper oxide was the only mixture to ignite by electrostatic discharge with minimum ignition energy (MIE) of 25 mJ and an electrical conductivity of 1246.25 nS; two orders of magnitude higher than the next composite. This study showed a similar trend in MIE for ignition triggered by a discharged spark compared with a thermal hot wire source.

Michael A. Daniels; Daniel J. Prentice; Chelsea Weir; Michelle L. Pantoya; Gautham Ramachandran; Tim Dallas

2013-02-01

270

An isoelastic prosthesis using a new composite material.  

PubMed

A new particulate composite material has been assessed with regard to the design of an 'isoelastic' or 'modulus matched' hip prosthesis. Three different prototype designs were assessed, each of which consisted of a femoral component made from the composite material, attached to a metal ball via a metal 'spike' insert. The prototypes varied in terms of the detailed shape of the spike, which was modified in the light of photoelastic stress analysis, so as to produce a more acceptable stress distribution to the composite material in the proximal region. Prototypes were made by hand moulding and by transfer moulding; both methods produced defects of various kinds. Simulation tests were conducted using a model of the proximal femur constructed from glass fibre composite, cyclically loaded in a servo-hydraulic testing machine. Though some difficulties were experienced with defective mouldings, especially for the transfer moulding process, a clear improvement was demonstrated for the final (Mark III) design. The fatigue endurance of this prototype was similar to that of conventional metal prostheses tested under similar conditions. Fatigue crack propagation tests were carried out on samples of the composite material to establish its propagation threshold. These results were combined with a finite element stress analysis and fracture mechanics theory to estimate the critical crack length for fatigue in this prosthesis. It was thus possible to specify the maximum safe size of defect that could be tolerated in use. PMID:8280313

Taylor, D; Martin, C; Cornelis, B; Jones, M E

1993-01-01

271

Optimizing material properties of composite plates for sound transmission problem  

NASA Astrophysics Data System (ADS)

To calculate the specific transmission loss (TL) of a composite plate, the conjugate gradient optimization method is utilized to estimate and optimize material properties of the composite plate in this study. For an n-layer composite plate, a nonlinear dynamic stiffness matrix based on the thick plate theory is formulated. To avoid huge computational efforts due to the combination of different composite material plates, a transfer matrix approach is proposed to restrict the dynamic stiffness matrix of the composite plate to a 4×4 matrix. Moreover, the transfer matrix approach has also been used to simplify the complexity of the objective function gradient for the optimization method. Numerical simulations are performed to validate the present algorithm by comparing the TL of the optimal composite plate with that of the original plate. Small number of iterations required during convergence tests illustrates the efficiency of the optimization method. The results indicate that an excellent estimation for the composite plate can be obtained for the desired sound transmission.

Tsai, Yu-Ting; Pawar, S. J.; Huang, Jin H.

2015-01-01

272

Experimental determination of material constants of a hybrid composite laminate  

SciTech Connect

This paper discusses the results of the experimental study that was conducted in order to determine the material properties of a hybrid composite laminate made from Fiberite material MXM-7714/120 (a fabric prepreg consisting of woven Kevlar{reg_sign} 49 reinforcement impregnated with Fiberite 250 F (121 C) curing 7714 epoxy resin) and HYE-2448AIE (a 250 F (121 C) curing epoxy resin impregnated unidirectional graphite tape). First, each of the materials that comprise the hybrid laminate was fabricated separately according to ASTM-D-3039 specification in order to determine their material properties. The materials were then hybridized and the properties were determined. Data from this experiment reveal that a new class of material that can meet desired specifications can be created through hybridization. The data also revealed that the properties of the materials bonded together as a hybrid complement the properties of the constituent members of the hybrid.

Ihekweazu, S.N.; Lari, S.B.; Unanwa, C.O. [South Carolina State Univ., Orangeburg, SC (United States)

1999-07-01

273

Development and Analysis of Synthetic Composite Materials Emulating Patient AAA Wall Material Properties  

NASA Astrophysics Data System (ADS)

Abdominal Aortic Aneurysm (AAA) rupture accounts for 14,000 deaths a year in the United States. Since the number of ruptures has not decreased significantly in recent years despite improvements in imaging and surgical procedures, there is a need for an accurate, noninvasive technique capable of establishing rupture risk for specific patients and discriminating lesions at high risk. In this project, synthetic composite materials replicating patient-specific wall stiffness and strength were developed and their material properties evaluated. Composites utilizing various fibers were developed to give a range of stiffness from 1825.75 kPa up through 8187.64 kPa with one base material, Sylgard 170. A range of strength from 631.12 kPa to 1083 kPa with the same base material was also found. By evaluating various base materials and various reinforcing fibers, a catalogue of stiffnesses and strengths was started to allow for adaptation to specific patient properties. Three specific patient properties were well-matched with two composites fabricated: silk thread-reinforced Sylgard 170 and silk thread-reinforced Dragon Skin 20. The composites showed similar stiffnesses to the specific patients while reaching target stresses at particular strains. Not all patients were matched with composites as of yet, but recommendations for future matches are able to be determined. These composites will allow for the future evaluation of flow-induced wall stresses in models replicating patient material properties and geometries.

Margossian, Christa M.

274

CI2 Composite materials for lithium battery application: influence of processing and composition on electrochemical performance  

Microsoft Academic Search

In the field of electrodes for lithium batteries, the most important present advances deal with new families of active materials and new principles of energy storage in these materials. Very scarce research is devoted to the composite electrode as a whole however. The electrode is in fact a very complex medium that needs to bring efficiently the ionic reactants (Li+

D. Guy; E. Ligneel; V. Gaudefroy; B. Lestriez; R. Bouchet; D. Guyomartd

275

DNA hybridization to compare species compositions of natural bacterioplankton assemblages.  

PubMed

Little is known about the species composition and variability of natural bacterial communities, mostly because conventional identification requires pure cultures, but less than 1% of active natural bacteria are cultivable. This problem was circumvented by comparing species compositions via hybridization of total DNA of natural bacterioplankton communities for the estimation of the fraction of DNA in common between two samples (similarity). DNA probes that were labeled with 35S by nick translation were hybridized to filter-bound DNA in a reciprocal fashion; similarities (in percent) were calculated by normalizing the values to self-hybridizations. In tests with DNA mixtures of pure cultures, the experimentally observed similarities agreed with expectations. However, reciprocal similarities (probe and target reversed) were often asymmetric, unlike those of DNA from single strains. This was due to the relative complexity and G + C content of DNA, which provided a means to interpret the asymmetry that was occasionally observed in natural samples. Natural bacteria were collected by filtration from Long Island Sound (LIS), N.Y., the Caribbean and Sargasso seas, and a coral reef lagoon near Bermuda. The samples showed similarities of less than 10 to 95%. The LIS and Sargasso and Caribbean sea samples were 20 to 50% similar to each other. The coral reef sample was less than 10% similar to the others, indicating its unique composition. Seasonality was also observed; an LIS sample obtained in the autumn was 40% similar to two LIS samples obtained in the summer; these latter two samples were 95% similar. We concluded that total DNA hybridization is a rapid, simple, and unbiased method for investigating the variation of bacterioplankton species composition over time and space, avoiding the need of culturing. PMID:2317044

Lee, S; Fuhrman, J A

1990-03-01

276

Mechanical and Material Properties of Metal Matrix Composite Conducting Alloys  

Microsoft Academic Search

The contact resistance and wear behavior of conducting contact surfaces is a function of hardness, applied load and material constituents. This paper presents mechanical and material properties of conducting alloys fabricated as functionally graded metal matrix composites (MMCs); in particular copper\\/tungsten, copper\\/tungsten carbide, and bronze\\/tungsten-carbide. Tungsten and in particular tungsten-carbide reinforcing particles are attractive in this application for their high

Lloyd Brown; Peter Joyce; Andrea Lazzarro

2010-01-01

277

Interdisciplinary research concerning the nature and properties of ceramic materials  

NASA Technical Reports Server (NTRS)

The nature and properties of ceramic materials as they relate to solid state physics and metallurgy are studied. Special attention was given to the applications of ceramics to NASA programs and national needs.

1975-01-01

278

Modeling the Mechanical Behavior of Ceramic Matrix Composite Materials  

NASA Technical Reports Server (NTRS)

Ceramic matrix composites are ceramic materials, such as SiC, that have been reinforced by high strength fibers, such as carbon. Designers are interested in using ceramic matrix composites because they have the capability of withstanding significant loads while at relatively high temperatures (in excess of 1,000 C). Ceramic matrix composites retain the ceramic materials ability to withstand high temperatures, but also possess a much greater ductility and toughness. Their high strength and medium toughness is what makes them of so much interest to the aerospace community. This work concentrated on two different tasks. The first task was to do an extensive literature search into the mechanical behavior of ceramic matrix composite materials. This report contains the results of this task. The second task was to use this understanding to help interpret the ceramic matrix composite mechanical test results that had already been obtained by NASA. Since the specific details of these test results are subject to the International Traffic in Arms Regulations (ITAR), they are reported in a separate document (Jordan, 1997).

Jordan, William

1998-01-01

279

NATURE MATERIALS | ADVANCE ONLINE PUBLICATION | www.nature.com/naturematerials 1 news & views  

E-print Network

NATURE MATERIALS | ADVANCE ONLINE PUBLICATION | www.nature.com/naturematerials 1 news & views S kin-human' in the science- fiction movie Metropolis or the sentient android Data in Star Trek. Engineers and materials coloured pixels were realized on a polyimide substrate, resulting in a free-standing, flexible electronic

Rogers, John A.

280

Compendium of Material Composition Data for Radiation Transport Modeling  

SciTech Connect

Computational modeling of radiation transport problems including homeland security, radiation shielding and protection, and criticality safety all depend upon material definitions. This document has been created to serve two purposes: 1) to provide a quick reference of material compositions for analysts and 2) a standardized reference to reduce the differences between results from two independent analysts. Analysts are always encountering a variety of materials for which elemental definitions are not readily available or densities are not defined. This document provides a location where unique or hard to define materials will be located to reduce duplication in research for modeling purposes. Additionally, having a common set of material definitions helps to standardize modeling across PNNL and provide two separate researchers the ability to compare different modeling results from a common materials basis.

Williams, Ralph G.; Gesh, Christopher J.; Pagh, Richard T.

2006-10-31

281

Zirconia–hydroxyapatite composite material with micro porous structure  

Microsoft Academic Search

ObjectivesTitanium plates and apatite blocks are commonly used for restoring large osseous defects in dental and orthopedic surgery. However, several cases of allergies against titanium have been recently reported. Also, sintered apatite block does not possess sufficient mechanical strength. In this study, we attempted to fabricate a composite material that has mechanical properties similar to biocortical bone and high bioaffinity

Takuya Junior Matsumoto; Sang-Hyun An; Takuya Ishimoto; Takayoshi Nakano; Satoshi Imazato

2011-01-01

282

Characteristics of soft magnetic composite material under rotating magnetic fluxes  

Microsoft Academic Search

This paper reports the measurement of magnetic properties of the soft magnetic composite material SOMALOYTM 500 in a square sample under different patterns of flux density with 2D magnetic excitations. The test system, principle of measurement, magnetic power loss calculation, and methods of correction for misalignment of H surface sensing coils are presented. The experimental results show that although nominally

J. J. Zhong; Y. G. Guo; J. G. Zhu; Z. W. Lin

2006-01-01

283

Manufacture of composite electrochemical materials from suspended electrolytes  

NASA Astrophysics Data System (ADS)

New composite electrochemical materials on a metallic substrate synthesized from suspended electrolytes with additives of kaolin and bentonite powders of the nanosized fraction are studied. The limiting concentrations of the additives in the electrolyte that warrant the retention of the decorative and special properties of the microchromium coating are determined.

Plotnikova, O. G.; Mal'kova, M. Yu.; Gruzd, N. S.; Zadiranov, A. N.; Paretskii, V. M.

2013-12-01

284

Studies of heterogeneous samples and material composition by fluorescence XAFS  

Microsoft Academic Search

X-ray Absorption Fine Structure (XAFS) Spectroscopy has proven to be an important tool for studying the composition and structure of materials. One benefit of XAFS is that it can be applied to a wide variety of systems, including complex real-world samples such as those found in biology and the environment. Determination of the chemical speciation of toxic elements in the

Firouzeh Tannazi

2004-01-01

285

MALE MOLDING FABRICATION PROCESS DEVELOPMENT WITH COMPOSITE MATERIALS  

E-print Network

PENNSTATE _ MALE MOLDING FABRICATION PROCESS DEVELOPMENT WITH COMPOSITE MATERIALS Yooku Tachie. The advantage of female molding, which is typically used, is that it provides a smooth outer molded surface operation. Male molding is generally less labor intensive, and allows the beam to be fabricated as a single

Yener, Aylin

286

Aluminum-matrix composite materials with shungite rock fillers  

NASA Astrophysics Data System (ADS)

A method is proposed for the introduction of shungite rocks into aluminum melts by mechanical mixing with carriers, namely, aluminum granules and reactive titanium powders taking part in exothermic in situ reactions. The structures of composite materials with shungite rock additions are studied, and a stabilizing effect of these additions on dry sliding friction is revealed.

Kalashnikov, I. E.; Kovalevski, V. V.; Chernyshova, T. A.; Bolotova, L. K.

2010-11-01

287

A three dimensional calculation of elastic equilibrium for composite materials  

NASA Technical Reports Server (NTRS)

A compact scheme is applied to three-dimensional elasticity problems for composite materials, involving simple geometries. The mathematical aspects of this approach are discussed, in particular the iteration method. A vector processor code implementing the compact scheme is presented, and several numerical experiments are summarized.

Lustman, Liviu R.; Rose, Milton E.

1986-01-01

288

Numerical Simulation of Delamination Growth in Composite Materials  

Microsoft Academic Search

Abstract The use of decohesion elements for the simulation of delamination in composite materials is reviewed The test methods available to measure the interfacial fracture toughness used in the formulation of decohesion elements are described initially After a brief presentation of the virtual crack closure technique, the technique most widely used to simulate delamination growth, the formulation of interfacial decohesion

P. P. Camanho; D. R. Ambur

2001-01-01

289

Efficient analysis of complex natural materials using LA-ICP-MS  

NASA Astrophysics Data System (ADS)

Many natural materials exhibit complex variations in chemical or isotopic composition over relatively short length scales, and these compositional variations often record important information about the environment or nature of the processes that lead to formation. Examples include complexly zoned crystals within volcanic rocks that record magmatic and volcanic signals, otoliths and other biominerals that record life history and environmental information, and speleothems that record climatic variables. Laser ablation ICP-MS analyses offer several advantages for quantifying compositional in chemically complex natural materials. These include the speed of analysis, the ability to sample at atmospheric pressures, the wide diversity of possible analytes, and the ability to make measurements in both spot and raster modes. The latter in particular offers advantages for analyses that require efficient acquisition of information over significant length scales, as in raster mode compositional data can be rapidly obtained by translating the laser laterally over a compositional variable material during a single analysis. In this fashion elemental or isotopic composition at a given analysis time corresponds to the lateral spatial dimension. This contrasts with a record obtained by a row of individual spots, which require a large number of discrete analyses, and requires significantly more analysis time. However there are also disadvantages to this style of analysis. Translation of the circular spots typically used for analysis results in significant signal attenuation and production of artifacts that may mirror natural diffusion profiles or other gradual changes. The ability to ablate using non-circular spots significantly reduces this effect, although the degree of attenuation is also increased by slower ablation cell response times. For single volume cells this may result in 50-100% additional attenuation than that produced by the translation of the spot alone, although two-volume and other rapid response cells significantly reduce this effect. Raster analyses are also highly sensitive to the presence of small contaminant phases along the raster trajectory, as the compositional signal from these can become attenuated and difficult to distinguish from natural compositional variations. It can also be difficult to establish exactly where compositional changes occur in materials that are visually homogenous. In this contribution we discuss these issues in more detail and present data acquisition and processing strategies that minimize these difficulties.

Kent, A. J.; Loewen, M. W.; Koleszar, A. M.; Miller, J.; Ungerer, C. "

2011-12-01

290

Assessment of space environment induced microdamage in toughened composite materials  

NASA Technical Reports Server (NTRS)

The effects of simulated space environments on the microdamage in a series of commercially available toughened matrix composite systems was determined. Low-earth orbit (LEO) exposures were simulated by thermal cycling; geosynchronous orbit (GEO) exposures were simulated by electron irradiation plus thermal cycling. Material response was characterized by assessing the induced microcracking and its influence on chemical and mechanical property changes. All materials, including several advanced, tough thermoplastics microcracked when exposed to the simulated LEO environment except a 177 C cured single phase toughened epoxy composite. The GEO simulated environment produced microdamage in all materials. The results suggest that increased matrix toughness may not be the overriding factor leading to improved durability in the space environment.

Sykes, George F.; Funk, Joan G.; Slemp, Wayne S.

1986-01-01

291

Recent Advances and Developments in Composite Dental Restorative Materials  

PubMed Central

Composite dental restorations represent a unique class of biomaterials with severe restrictions on biocompatibility, curing behavior, esthetics, and ultimate material properties. These materials are presently limited by shrinkage and polymerization-induced shrinkage stress, limited toughness, the presence of unreacted monomer that remains following the polymerization, and several other factors. Fortunately, these materials have been the focus of a great deal of research in recent years with the goal of improving restoration performance by changing the initiation system, monomers, and fillers and their coupling agents, and by developing novel polymerization strategies. Here, we review the general characteristics of the polymerization reaction and recent approaches that have been taken to improve composite restorative performance. PMID:20924063

Cramer, N.B.; Stansbury, J.W.; Bowman, C.N.

2011-01-01

292

Application of Raman Spectroscopy for Nondestructive Evaluation of Composite Materials  

NASA Technical Reports Server (NTRS)

This paper will present an overview of efforts to investigate the application of Raman spectroscopy for the characterization of Kevlar materials. Raman spectroscopy is a laser technique that is sensitive to molecular interactions in materials such as Kevlar, graphite and carbon used in composite materials. The overall goal of this research reported here is to evaluate Raman spectroscopy as a potential nondestructive evaluation (NDE) tool for the detection of stress rupture in Kevlar composite over-wrapped pressure vessels (COPVs). Characterization of the Raman spectra of Kevlar yarn and strands will be presented and compared with analytical models provided in the literature. Results of testing to investigate the effects of creep and high-temperature aging on the Raman spectra will be presented.

Washer, Glenn A.; Brooks, Thomas M. B.; Saulsberry, Regor

2007-01-01

293

Natural Lignocellulosic Fibers as Engineering Materials—An Overview  

NASA Astrophysics Data System (ADS)

Recent investigations on the tensile properties of natural cellulose-based fibers revealed an increasing potential as engineering materials. This is particularly the case of very thin fibers of some species such as sisal, ramie, and curaua. However, several other commonly used fibers such as flax, jute, hemp, coir, cotton, and bamboo as well as less known bagasse, piassava, sponge gourde, and buriti display tensile properties that could qualify them as engineering materials. An overview of the strength limits attained by these fibers is presented. Based on a tensile strength vs density chart, it is shown that natural fibers stand out as a relevant class of engineering materials.

Monteiro, Sergio Neves; Lopes, Felipe Perissé Duarte; Barbosa, Anderson Paula; Bevitori, Alice Barreto; Silva, Isabela Leão Amaral Da; Costa, Lucas Lopes Da

2011-10-01

294

A Study of Failure Criteria of Fibrous Composite Materials  

NASA Technical Reports Server (NTRS)

The research described in this paper is focused on two areas: (1) evaluation of existing composite failure criteria in the nonlinear, explicit transient dynamic finite element code, MSC.Dytran, and (2) exploration of the possibilities for modification of material and failure models to account for large deformations, progressive failure, and interaction of damage accumulation with stress/strain response of laminated composites. Following a review of the MSC.Dytran user manual, a bibliographical review of existing failure criteria of composites was performed. The papers considered most interesting for the objective of this report are discussed in section 2. The failure criteria included in the code under consideration are discussed in section 3. A critical summary of the present procedures to perform analysis and design of composites is presented in section 4. A study of the most important historical failure criteria for fibrous composite materials and some of the more recent modifications proposed were studied. The result of this analysis highlighted inadequacies in the existing failure criteria and the need to perform some numerical analyses to elucidate the answer to questions on which some of the proposed criteria are based. A summary of these ideas, which is a proposal of studies to be developed, is presented in section 5. Finally, some ideas for future developments are summarized in section 6.

Paris, Federico; Jackson, Karen E. (Technical Monitor)

2001-01-01

295

Percolation modeling of self-damaging of composite materials  

NASA Astrophysics Data System (ADS)

We propose the concept of autonomous self-damaging in “smart” composite materials, controlled by activation of added nanosize “damaging” capsules. Percolation-type modeling approach earlier applied to the related concept of self-healing materials, is used to investigate the behavior of the initial material's fatigue. We aim at achieving a relatively sharp drop in the material's integrity after some initial limited fatigue develops in the course of the sample's usage. Our theoretical study considers a two-dimensional lattice model and involves Monte Carlo simulations of the connectivity and conductance in the high-connectivity regime of percolation. We give several examples of local capsule-lattice and capsule-capsule activation rules and show that the desired self-damaging property can only be obtained with rather sophisticated “smart” material's response involving not just damaging but also healing capsules.

Domanskyi, Sergii; Privman, Vladimir

2014-07-01

296

Contribution to the study of composite materials and their damage. Thesis - Paris VI Univ. - 1984  

NASA Technical Reports Server (NTRS)

Chapter 1 describes the homogenization techniques used for defining the overall behavior of composite materials for conventional cases of linear and perfectly glued elastic constituents. Chapters 2 and 3 focus on solving the problems inherent in two types of degenerated situations: elastic media with microcavities, and elastic media containing rigid inclusions. Through suitable definitions of deformation concepts and macroscopic stresses it is shown that conventional theory results apply naturally to these limits.

Lene, F.

1987-01-01

297

Nondestructive evaluation/characterization of composite materials and structures using the acousto-ultrasonic techniques  

NASA Technical Reports Server (NTRS)

This paper introduces the nature and the underlying rational of the acousto-ultrasonic stress wave factor technique and some of its applications to composite materials and structures. Furthermore, two examples of successful application of the acousto-ultrasonic technique are presented in detail. In the first example, the acousto-ultrasonic technique is used to evaluate the adhesive bond strength between rubber layers and steel plates, and in the seocnd example the tehcnique is used to monitor progressive damage in wire rope.

Dos Reis, H. L. M.; Vary, A.

1988-01-01

298

Trihalomethanes formed from natural organic matter isolates: Using isotopic and compositional data to help understand sources  

USGS Publications Warehouse

Over 20 million people drink water from the Sacramento-San Joaquin Delta despite problematic levels of natural organic matter (NOM) and bromide in Delta water, which can form trihalomethanes (THMs) during the treatment process. It is widely believed that NOM released from Delta peat islands is a substantial contributor to the pool of THM precursors present in Delta waters. Dissolved NOM was isolated from samples collected at five channel sites within the Sacramento-San Joaquin Rivers and Delta, California, USA, and from a peat island agricultural drain. To help understand the sources of THM precursors, samples were analyzed to determine their chemical and isotopic composition, their propensity to form THMs, and the isotopic composition of the THMs. The chemical composition of the isolates was quite variable, as indicated by significant differences in carbon-13 nuclear magnetic resonance spectra and carbon-to-nitrogen concentration ratios. The lowest propensity to form THMs per unit of dissolved organic carbon was observed in the peat island agricultural drain isolate, even though it possessed the highest fraction of aromatic material and the highest specific ultraviolet absorbance. Changes in the chemical and isotopic composition of the isolates and the isotopic composition of the THMs suggest that the source of the THMs precursors was different between samples and between isolates. The pattern of variability in compositional and isotopic data for these samples was not consistent with simple mixing of river- and peat-derived organic material.

Bergamaschi, B.A.; Fram, M.S.; Fujii, R.; Aiken, G.R.; Kendall, C.; Silva, S.R.

2000-01-01

299

Modular design in natural and biomimetic soft materials.  

PubMed

Under eons of evolutionary and environmental pressure, biological systems have developed strong and lightweight peptide-based polymeric materials by using the 20 naturally occurring amino acids as principal monomeric units. These materials outperform their man-made counterparts in the following ways: 1) multifunctionality/tunability, 2) adaptability/stimuli-responsiveness, 3) synthesis and processing under ambient and aqueous conditions, and 4) recyclability and biodegradability. The universal design strategy that affords these advanced properties involves "bottom-up" synthesis and modular, hierarchical organization both within and across multiple length-scales. The field of "biomimicry"-elucidating and co-opting nature's basic material design principles and molecular building blocks-is rapidly evolving. This Review describes what has been discovered about the structure and molecular mechanisms of natural polymeric materials, as well as the progress towards synthetic "mimics" of these remarkable systems. PMID:21898722

Kushner, Aaron M; Guan, Zhibin

2011-09-19

300

The weak interfaces within tough natural composites: experiments on three types of nacre.  

PubMed

Mineralization is a typical strategy used in natural materials to achieve high stiffness and hardness for structural functions such as skeletal support, protection or predation. High mineral content generally leads to brittleness, yet natural materials such as bone, mollusk shells or glass sponge achieve relatively high toughness considering the weakness of their constituents through intricate microstructures. In particular, nanometers thick organic interfaces organized in micro-architectures play a key role in providing toughness by various processes including crack deflection, crack bridging or energy dissipation. While these interfaces are critical in these materials, their composition, structure and mechanics is often poorly understood. In this work we focus on nacre, one of the most impressive hard biological materials in terms of toughness. We performed interfacial fracture tests on chevron notched nacre samples from three different species: red abalone, top shell and pearl oyster. We found that the intrinsic toughness of the interfaces is indeed found to be extremely low, in the order of the toughness of the mineral inclusions themselves. Such low toughness is required for the cracks to follow the interfaces, and to deflect and circumvent the mineral tablets. This result highlights the efficacy of toughening mechanisms in natural materials, turning low-toughness inclusions and interfaces into high-performance composites. We found that top shell nacre displayed the highest interfacial toughness, because of higher surface roughness and a more resilient organic material, and also through extrinsic toughening mechanisms including crack deflection, crack bridging and process zone. In the context of biomimetics, the main implication of this finding is that the interface in nacre-like composite does not need to be tough; the extensibility or ductility of the interfaces may be more important than their strength and toughness to produce toughness at the macroscale. PMID:23084045

Khayer Dastjerdi, Ahmad; Rabiei, Reza; Barthelat, Francois

2013-03-01

301

The aqueous corrosion behavior of technetium - Alloy and composite materials  

SciTech Connect

Metal waste forms are under study as possible disposal forms for technetium and other fission products. The alloying of Tc is desirable to reduce the melting point of the Tc-containing metal waste form and potentially improve its corrosion resistance. Technetium-nickel composites were made by mixing the two metal powders and pressing the mixture to make a pellet. The as-pressed composite materials were compared to sintered composites and alloys of identical composition in electrochemical corrosion tests. As-pressed samples were not robust enough for fine polishing and only a limited number of corrosion tests were performed. Alloys and composites with 10 wt% Tc appear to be more corrosion resistant at open circuit than the individual components based on linear polarization resistance and polarization data. The addition of 10 wt% Tc to Ni appears beneficial at open circuit, but detrimental upon anodic polarization. Qualitatively, the polarizations of 10 wt% Tc alloys and composites appear like crude addition of Tc plus Ni. The 1 wt% Tc alloys behave like pure Ni, but some effect of Tc is seen upon polarization. Cathodic polarization of Tc by Ni appears feasible based on open circuit potential measurements, however, zero resistance ammetry and solution measurements are necessary to confirm cathodic protection.

Jarvinen, G.; Kolman, D.; Taylor, C.; Goff, G.; Cisneros, M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Mausolf, E.; Poineau, F.; Koury, D.; Czerwinski, K. [Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, NV 89154 (United States)

2013-07-01

302

Elastoplastic analysis of thermal cycling: Layered materials with compositional gradients  

SciTech Connect

Elastoplastic analyses are presented for the cyclic thermal response in multi-layered materials which comprise layers of fixed compositions of a metal and a ceramic, and a compositionally graded interface. Analytical solutions for the characteristic temperature at which the onset of thermally induced plastic deformation occurs are derived for the layered composite. Solutions for the evolution of curvature and thermal strains, and for the initiation of plastic yielding are also obtained for different combinations of the geometry, physical properties and compositional gradation for both thermoelastic and thermoplastic deformation. Finite-element formulations incorporating continuous and smooth spatial variations in the composition and properties of the graded layer are used to simulate the evolution of thermal stresses, the accumulation of plastic strains, and the development of monotonic and cyclic plastic zones at the interfaces, edges and free surfaces of different layers during thermal cycling. Engineering diagrams detailing the effects of compositional gradients are also presented for optimizing thermal residual stresses, layer geometry, and plastic strain accumulation.

Giannakopulos, A.E.; Olsson, M. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Solid Mechanics] [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Solid Mechanics; Suresh, S.; Finot, M. [Massachusetts Inst. of Tech., Cambridge, MA (United States)] [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1995-04-01

303

Composite smart materials using high-volume microelectronics fabrication techniques  

NASA Astrophysics Data System (ADS)

Smart materials, containing sensors, actuators and processing electronics, are of great potential use in defense and commercial applications from acoustic stealth to medial imaging. While 1:3 composites using PZT rods are now available commercially in limited quantities, composites with individually addressable actuator and sensor arrays are not, nor have conditioning and processing electronics been embedded in the same material. There are several technical and cost reasons for this, including the complexity of interconnections, capacitance of individual elements, thermal dissipation, and the expense of fabricating the material. We have been developing composite materials comprising arrays of miniature actuators fabricated using surface mount capacitor technology, and amenable to automated fabrication using `pick and place' techniques. Miniature actuators with up to 0.1% strain, and operating at 30 V bias and ac swing of +/- 30 V have been fabricated, and placed in 10-by- 10 actuator arrays on Kapton sheets on which circuits have been printed. The arrays were then `potted' in RTV liquid rubbers. Individual actuator motion and multiple actuator influence functions were measured as a function of applied voltage and adjacent actuator motion. These results, along with in-water performance (source level and directivity), are presented.

Winzer, Stephen R.; Shankar, Natarajan; Caldwell, Paul J.; May, Russell G.

1995-05-01

304

Experimental and Analytical Characterization of the Macromechanical Response for Triaxial Braided Composite Materials  

NASA Technical Reports Server (NTRS)

Increasingly, carbon composite structures are being used in aerospace applications. Their highstrength, high-stiffness, and low-weight properties make them good candidates for replacing many aerospace structures currently made of aluminum or steel. Recently, many of the aircraft engine manufacturers have developed new commercial jet engines that will use composite fan cases. Instead of using traditional composite layup techniques, these new fan cases will use a triaxially braided pattern, which improves case performance. The impact characteristics of composite materials for jet engine fan case applications have been an important research topic because Federal regulations require that an engine case be able to contain a blade and blade fragments during an engine blade-out event. Once the impact characteristics of these triaxial braided materials become known, computer models can be developed to simulate a jet engine blade-out event, thus reducing cost and time in the development of these composite jet engine cases. The two main problems that have arisen in this area of research are that the properties for these materials have not been fully determined and computationally efficient computer models, which incorporate much of the microscale deformation and failure mechanisms, are not available. The research reported herein addresses some of the deficiencies present in previous research regarding these triaxial braided composite materials. The current research develops new techniques to accurately quantify the material properties of the triaxial braided composite materials. New test methods are developed for the polymer resin composite constituent and representative composite coupons. These methods expand previous research by using novel specimen designs along with using a noncontact measuring system that is also capable of identifying and quantifying many of the microscale failure mechanisms present in the materials. Finally, using the data gathered, a new hybrid micromacromechanical computer model is created to simulate the behavior of these composite material systems under static and ballistic impact loading using the test data acquired. The model also quantifies the way in which the fiber/matrix interface affects material response under static and impact loading. The results show that the test methods are capable of accurately quantifying the polymer resin under a variety of strain rates and temperature for three loading conditions. The resin strength and stiffness data show a clear rate and temperature dependence. The data also show the hydrostatic stress effects and hysteresis, all of which can be used by researchers developing composite constitutive models for the resins. The results for the composite data reveal noticeable differences in strength, failure strain, and stiffness in the different material systems presented. The investigations into the microscale failure mechanisms provide information about the nature of the different material system behaviors. Finally, the developed computer model predicts composite static strength and stiffness to within 10 percent of the gathered test data and also agrees with composite impact data, where available.

Littell, Justin D.

2013-01-01

305

Untethered micro-robotic coding of three-dimensional material composition.  

PubMed

Complex functional materials with three-dimensional micro- or nano-scale dynamic compositional features are prevalent in nature. However, the generation of three-dimensional functional materials composed of both soft and rigid microstructures, each programmed by shape and composition, is still an unsolved challenge. Here we describe a method to code complex materials in three-dimensions with tunable structural, morphological and chemical features using an untethered magnetic micro-robot remotely controlled by magnetic fields. This strategy allows the micro-robot to be introduced to arbitrary microfluidic environments for remote two- and three-dimensional manipulation. We demonstrate the coding of soft hydrogels, rigid copper bars, polystyrene beads and silicon chiplets into three-dimensional heterogeneous structures. We also use coded microstructures for bottom-up tissue engineering by generating cell-encapsulating constructs. PMID:24469115

Tasoglu, S; Diller, E; Guven, S; Sitti, M; Demirci, U

2014-01-01

306

Anode materials for sour natural gas solid oxide fuel cells  

NASA Astrophysics Data System (ADS)

Novel anode catalysts have been developed for sour natural gas solid oxide fuel cell (SOFC) applications. Sour natural gas comprises light hydrocarbons, and typically also contains H2S. An alternative fuel SOFC that operates directly on sour natural gas would reduce the overall cost of plant construction and operation for fuel cell power generation. The anode for such a fuel cell must have good catalytic and electrocatalytic activity for hydrocarbon conversion, sulfur-tolerance, resistance to coking, and good electronic and ionic conductivity. The catalytic activity and stability of ABO3 (A= La, Ce and/or Sr, B=Cr and one or more of Ti, V, Cr, Fe, Mn, or Co) perovskites as SOFC anode materials depends on both A and B, and are modified by substituents. The materials have been prepared by both solid state and wet-chemical methods. The physical and chemical characteristics of the materials have been fully characterized using electron microscopy, XRD, calorimetry, dilatometry, particle size and area, using XPS and TGA-DSC-MS. Electrochemical performance was determined using potentiodynamic and potentiostatic cell testing, electrochemical impedance analysis, and conductivity measurements. Neither Ce0.9Sr0.1VO3 nor Ce0.9 Sr0.1Cr0.5V0.5O3 was an active anode for oxidation of H2 and CH4 fuels. However, active catalysts comprising Ce0:9Sr0:1V(O,S)3 and Ce0.9Sr 0.1Cr0.5V0.5(O,S)3 were formed when small concentrations of H2S were present in the fuels. The oxysulfides formed in-situ were very active for conversion of H2S. The maximum performance improved from 50 mW cm-2 to 85 mW cm -2 in 0.5% H2S/CH4 at 850°C with partial substitution of V by Cr in Ce0.9Sr0.1V(O,S)3. Selective conversion of H2S offers potential for sweetening of sour gas without affecting the hydrocarbons. Perovskites La0.75Sr0.25Cr0.5X 0.5O3--delta, (henceforth referred to as LSCX, X=Ti, Mn, Fe, Co) are active for conversion of H2, CH4 and 0.5% H2S/CH4. The order of activity in the different fuels depends on the substituent element: CH4, X = Fe>Mn>Ti; H 2, X = Fe>Mn>Ti; and 0.5% H2S/CH4, X = Fe>Ti>Mn. The electrocatalytic activity for methane oxidation in a fuel cell correlates with ex-situ temperature programmed catalytic activity. A process is proposed to explain the difference in catalyst order and enhanced activities in H 2S/CH4 as fuel compared to CH4 alone. The maximum power density of 250 mW cm-2 was attained using a fuel cell with a composite anode, LSCFe-GDC | YSZ(0.3 mm) | Pt, operated at 850°C (GDC is Ce0.9Gd0.1O3, a good mixed conductor under reducing conditions).

Danilovic, Nemanja

307

Compendium of Material Composition Data for Radiation Transport Modeling  

SciTech Connect

Introduction Meaningful simulations of radiation transport applications require realistic definitions of material composition and densities. When seeking that information for applications in fields such as homeland security, radiation shielding and protection, and criticality safety, researchers usually encounter a variety of materials for which elemental compositions are not readily available or densities are not defined. Publication of the Compendium of Material Composition Data for Radiation Transport Modeling, Revision 0, in 2006 was the first step toward mitigating this problem. Revision 0 of this document listed 121 materials, selected mostly from the combined personal libraries of staff at the Pacific Northwest National Laboratory (PNNL), and thus had a scope that was recognized at the time to be limited. Nevertheless, its creation did provide a well-referenced source of some unique or hard-to-define material data in a format that could be used directly in radiation transport calculations being performed at PNNL. Moreover, having a single common set of material definitions also helped to standardize at least one aspect of the various modeling efforts across the laboratory by providing separate researchers the ability to compare different model results using a common basis of materials. The authors of the 2006 compendium understood that, depending on its use and feedback, the compendium would need to be revised to correct errors or inconsistencies in the data for the original 121 materials, as well as to increase (per users suggestions) the number of materials listed. This 2010 revision of the compendium has accomplished both of those objectives. The most obvious change is the increased number of materials from 121 to 372. The not-so-obvious change is the mechanism used to produce the data listed here. The data listed in the 2006 document were compiled, evaluated, entered, and error-checked by a group of individuals essentially by hand, providing no library file or mechanism for revising the data in a consistent and traceable manner. The authors of this revision have addressed that problem by first compiling all of the information (i.e., numbers and references) for all the materials into a single database, maintained at PNNL, that was then used as the basis for this document.

McConn, Ronald J.; Gesh, Christopher J.; Pagh, Richard T.; Rucker, Robert A.; Williams III, Robert

2011-03-04

308

DOE/MSU composite material fatigue database: Test methods, materials, and analysis  

SciTech Connect

This report presents a detailed analysis of the results from fatigue studies of wind turbine blade composite materials carried out at Montana State University (MSU) over the last seven years. It is intended to be used in conjunction with the DOE/MSU composite Materials Fatigue Database. The fatigue testing of composite materials requires the adaptation of standard test methods to the particular composite structure of concern. The stranded fabric E-glass reinforcement used by many blade manufacturers has required the development of several test modifications to obtain valid test data for materials with particular reinforcement details, over the required range of tensile and compressive loadings. Additionally, a novel testing approach to high frequency (100 Hz) testing for high cycle fatigue using minicoupons has been developed and validated. The database for standard coupon tests now includes over 4,100 data points for over 110 materials systems. The report analyzes the database for trends and transitions in static and fatigue behavior with various materials parameters. Parameters explored are reinforcement fabric architecture, fiber content, content of fibers oriented in the load direction, matrix material, and loading parameters (tension, compression, and reversed loading). Significant transitions from good fatigue resistance to poor fatigue resistance are evident in the range of materials currently used in many blades. A preliminary evaluation of knockdowns for selected structural details is also presented. The high frequency database provides a significant set of data for various loading conditions in the longitudinal and transverse directions of unidirectional composites out to 10{sup 8} cycles. The results are expressed in stress and strain based Goodman Diagrams suitable for design. A discussion is provided to guide the user of the database in its application to blade design.

Mandell, J.F.; Samborsky, D.D. [Montana State Univ., Bozeman, MT (United States). Dept. of Chemical Engineering

1997-12-01

309

Power loss separation in Fe-based composite materials  

NASA Astrophysics Data System (ADS)

The frequency dependence of total losses measured in the frequency range from dc to 1 kHz of two Fe-based soft magnetic composites (prepared by compaction of an ASC 100.29 iron powder mixture with 10 vol% of commercial thermoset resin and of a Somaloy® 700 powder) was analyzed. We found out that hysteresis losses (per volume unit) are higher for the composite with lower volume concentration of iron particles (i.e. mixture of iron with resin) and consequently weaker magnetic interaction between particles. On the other hand, higher specific resistivity of the sample with lower magnetic fraction causes lower contribution of eddy current losses to the total losses. A linear dependence of the total energy losses on frequency was observed and from them the contribution of excess losses was obtained. The detailed study of the excess losses resulted in an explanation of the frequency dependence of these losses in composite materials.

Kollár, Peter; Bir?áková, Zuzana; Füzer, Ján; Bureš, Radovan; Fáberová, Mária

2013-02-01

310

Effective thermal conductivity of a thin, randomly oriented composite material  

SciTech Connect

The thermal conductivity of a randomly oriented composite material is modeled using a probabilistic approach in order to determine if a size effect exists for the thermal conductivity at small composite thicknesses. The numerical scheme employs a random number generator to position the filler elements, which have a relatively high thermal conductivity, within a matrix having a relatively low thermal conductivity. The results indicate that, below some threshold thickness, the composite thermal conductivity increases with decreasing thickness, while above the threshold the thermal conductivity is independent of thickness. The threshold thickness increases for increasing filler fraction and increasing k{sub f}/k{sub m}, the ratio between the filler and matrix thermal conductivities.

Phelan, P.E.; Niemann, R.C.

1997-07-01

311

Mechanical properties of Al-mica particulate composite material  

NASA Technical Reports Server (NTRS)

Cast aluminum alloy mica particle composites of varying mica content were tested in tension, compression, and impact. With 2.2 percent mica (size range 40-120 microns) the tensile and compression strengths of aluminum alloy decreased by 56 and 22 percent, respectively. The corresponding decreases in percent elongation and percent reduction are 49 and 39 percent. Previous work shows that despite this decrease in strength the composite with 2.5 percent mica and having an UTS of 15 kg/sq mm and compression strength of 28 kg/sq mm performs well as a bearing material under severe running conditions. The differences in strength characteristics of cast aluminum-mica particle composites between tension and compression suggests that, as in cast iron, expansion of voids at the matrix particle interface may be the guiding mechanism of the deformation. SEM studies show that on the tensile fractured specimen surface, there are large voids at the particle matrix interface.

Nath, D.; Bhatt, R. T.; Rohatgi, P. K.; Biswas, S. K.

1980-01-01

312

27 CFR 555.221 - Requirements for display fireworks, pyrotechnic compositions, and explosive materials used in...  

Code of Federal Regulations, 2013 CFR

...false Requirements for display fireworks, pyrotechnic compositions, and explosive materials used in assembling fireworks or articles pyrotechnic. 555...221 Requirements for display fireworks, pyrotechnic compositions,...

2013-04-01

313

27 CFR 555.221 - Requirements for display fireworks, pyrotechnic compositions, and explosive materials used in...  

Code of Federal Regulations, 2014 CFR

...false Requirements for display fireworks, pyrotechnic compositions, and explosive materials used in assembling fireworks or articles pyrotechnic. 555...221 Requirements for display fireworks, pyrotechnic compositions,...

2014-04-01

314

27 CFR 555.221 - Requirements for display fireworks, pyrotechnic compositions, and explosive materials used in...  

Code of Federal Regulations, 2012 CFR

... true Requirements for display fireworks, pyrotechnic compositions, and explosive materials used in assembling fireworks or articles pyrotechnic. 555...221 Requirements for display fireworks, pyrotechnic compositions,...

2012-04-01

315

Material properties and fractography of an indirect dental resin composite  

PubMed Central

Objectives Determination of material and fractographic properties of a dental indirect resin composite material. Methods A resin composite (Paradigm, 3M-ESPE, MN) was characterized by strength, static elastic modulus, Knoop hardness, fracture toughness and edge toughness. Fractographic analyses of the broken bar surfaces was accomplished with a combination of optical and SEM techniques, and included determination of the type and size of the failure origins, and fracture mirror and branching constants. Results The flexure test mean strength ± standard deviation was 145 MPA ± 17 MPa, and edge toughness, Te, was 172 N/mm ±12 N/mm. Knoop hardness was load dependent, with a plateau at 0.99 GPa ± .02 GPa. Mirrors in the bar specimens were measured with difficulty, resulting in a mirror constant of approximately 2.6 MPa·m1/2. Fracture in the bar specimens initiated at equiaxed material flaws that had different filler concentrations that sometimes were accompanied by partial microcracks. Using the measured flaw sizes, which ranged from 35 µm to 100 µm in size, and estimates of the stress intensity shape factors, fracture toughness was estimated to be 1.1 MPa·m1/2 ± 0.2 MPa·m1/2. Significance Coupling the flexure tests with fractographic examination enabled identification of the intrinsic strength limiting flaws. The same techniques could be useful in determining if clinical restorations of similar materials fail from the same causes. The existence of a strong load-dependence of the Knoop hardness of the resin composite is not generally mentioned in the literature, and is important for material comparisons and wear evaluation studies. Finally, the edge toughness test was found promising as a quantitative measure of resistance to edge chipping, an important failure mode in this class of materials. PMID:20304478

Quinn, Janet B.; Quinn, George D.

2011-01-01

316

A fast multipole hybrid boundary node method for composite materials  

NASA Astrophysics Data System (ADS)

This article presents a multi-domain fast multipole hybrid boundary node method for composite materials in 3D elasticity. The hybrid boundary node method (hybrid BNM) is a meshless method which only requires nodes constructed on the surface of a domain. The method is applied to 3D simulation of composite materials by a multi-domain solver and accelerated by the fast multipole method (FMM) in this paper. The preconditioned GMRES is employed to solve the final system equation and precondition techniques are discussed. The matrix-vector multiplication in each iteration is divided into smaller scale ones at the sub-domain level and then accelerated by FMM within individual sub-domains. The computed matrix-vector products at the sub-domain level are then combined according to the continuity conditions on the interfaces. The algorithm is implemented on a computer code written in C + +. Numerical results show that the technique is accurate and efficient.

Wang, Qiao; Miao, Yu; Zhu, Hongping

2013-06-01

317

Degradation, fatigue and failure of resin dental composite materials  

PubMed Central

The intent of this article is to review the numerous factors that affect the mechanical properties of particle or fiber filler containing, indirect dental resin composite materials. The focus will be on degradation due to aging in different media, mainly water and water and ethanol, cyclic loading, and mixed mode loading on the flexure strength and fracture toughness. Next several selected papers will be examined in detail with respect to mixed and cyclic loading and then an examination of 3D tomography using multiaxial compression specimens. The main cause of failure, for most dental resin composites, is the breakdown of the resin matrix and or the interface between the filler and the resin matrix. In clinical studies, it appears that failure in the first 5 years is a restoration issue (technique or material selection) and after that time period from secondary decay. PMID:18650540

Drummond, James L.

2008-01-01

318

Characterization of carbon fiber composite materials for RF applications  

NASA Astrophysics Data System (ADS)

Carbon Fiber Composite (CFC) materials have been used for decades in the aerospace, automotive, and naval industries. They have often been used because of their mechanical advantages. These advantageous characteristics have typically included low weight and high strength. It is also a benefit that CFC materials can be made into nearly any shape or size. With the abundant use of CFC materials, it seems desirable to better under- stand the electromagnetic applications of these materials. CFC materials consist of a non-conductive resin or epoxy in addition to conductive carbon fibers. The carbon fibers can be oriented and layered in many different configurations. The specific orientation and layering of the carbon fibers has a direct impact on its electrical characteristics. One specific characteristic of interest is the conductivity of CFC materials. The work in this paper deals with probing the conductivity characteristics of CFC materials for applications in antenna and radar design. Multiple layouts of carbon fiber are investigated. The DC conductivity was measured by applying a conductive epoxy to sample edges and using a milliohm meter. Shielding effectiveness was then predicted based on fundamental electromagnetics for conducting media. Finally, prototype dipole antennas made from CFC materials were investigated.

Riley, Elliot J.; Lenzing, Erik H.; Narayanan, Ram M.

2014-05-01

319

Ultrasonic and radiographic evaluation of advanced aerospace materials: Ceramic composites  

NASA Technical Reports Server (NTRS)

Two conventional nondestructive evaluation techniques were used to evaluate advanced ceramic composite materials. It was shown that neither ultrasonic C-scan nor radiographic imaging can individually provide sufficient data for an accurate nondestructive evaluation. Both ultrasonic C-scan and conventional radiographic imaging are required for preliminary evaluation of these complex systems. The material variations that were identified by these two techniques are porosity, delaminations, bond quality between laminae, fiber alignment, fiber registration, fiber parallelism, and processing density flaws. The degree of bonding between fiber and matrix cannot be determined by either of these methods. An alternative ultrasonic technique, angular power spectrum scanning (APSS) is recommended for quantification of this interfacial bond.

Generazio, Edward R.

1990-01-01

320

Composite material from recycled polyester for recyclable automobile structures  

SciTech Connect

DuPont has developed a compression-moldable composite made from the thermoplastic polyester PET and long glass fibers. This material, XTC{trademark}, is part of the class of materials known as GMT`s, or glass-mat thermoplastics. The PET content in XTC{trademark} allows the use of a wide variety of recycled material that might otherwise end up in landfills and incinerators. DuPont has succeeded in using 100% post-consumer polyester, from bottles, film, or fibers, in the composite. Since processing involves heating the material to the melt in air, the main technical issues are hydrolysis and oxidative degradation. Impurities in the recycled material must be carefully monitored, as they often increase the extent of degradation. The product itself, used to mold shaped structures and body panels for automobiles, may be recycled after its useful life. Depending on the needed purity level, processes ranging from injection molding to methanolysis can turn ground XTC{trademark} parts back into new, useful products.

Lertola, J.G. [DuPont Company, Newark, DE (United States)

1995-12-31

321

Modeling Lightning Impact Thermo-Mechanical Damage on Composite Materials  

NASA Astrophysics Data System (ADS)

Carbon fiber-reinforced polymers, used in primary structures for aircraft due to an excellent strength-to-weight ratio when compared with conventional aluminium alloy counterparts, may nowadays be considered as mature structural materials. Their use has been extended in recent decades, with several aircraft manufacturers delivering fuselages entirely manufactured with carbon composites and using advanced processing technologies. However, one of the main drawbacks of using such composites entails their poor electrical conductivity when compared with aluminium alloy competitors that leads to lightning strikes being considered a significant threat during the service life of the aircraft. Traditionally, this problem was overcome with the use of a protective copper/bronze mesh that added additional weight and reduced the effectiveness of use of the material. Moreover, this traditional sizing method is based on vast experimental campaigns carried out by subjecting composite panels to simulated lightning strike events. While this method has proven its validity, and is necessary for certification of the structure, it may be optimized with the aid provided by physically based numerical models. This paper presents a model based on the finite element method that includes the sources of damage observed in a lightning strike, such as thermal damage caused by Joule overheating and electromagnetic/acoustic pressures induced by the arc around the attachment points. The results of the model are compared with lightning strike experiments carried out in a carbon woven composite.

Muñoz, Raúl; Delgado, Sofía; González, Carlos; López-Romano, Bernardo; Wang, De-Yi; LLorca, Javier

2014-02-01

322

Probability techniques for reliability analysis of composite materials  

NASA Technical Reports Server (NTRS)

Traditional design approaches for composite materials have employed deterministic criteria for failure analysis. New approaches are required to predict the reliability of composite structures since strengths and stresses may be random variables. This report will examine and compare methods used to evaluate the reliability of composite laminae. The two types of methods that will be evaluated are fast probability integration (FPI) methods and Monte Carlo methods. In these methods, reliability is formulated as the probability that an explicit function of random variables is less than a given constant. Using failure criteria developed for composite materials, a function of design variables can be generated which defines a 'failure surface' in probability space. A number of methods are available to evaluate the integration over the probability space bounded by this surface; this integration delivers the required reliability. The methods which will be evaluated are: the first order, second moment FPI methods; second order, second moment FPI methods; the simple Monte Carlo; and an advanced Monte Carlo technique which utilizes importance sampling. The methods are compared for accuracy, efficiency, and for the conservativism of the reliability estimation. The methodology involved in determining the sensitivity of the reliability estimate to the design variables (strength distributions) and importance factors is also presented.

Wetherhold, Robert C.; Ucci, Anthony M.

1994-01-01

323

Composite slip table of dissimilar materials for damping longitudinal modes  

DOEpatents

A vibration slip table for use in a vibration testing apparatus. The table s comprised of at least three composite layers of material; a first metal layer, a second damping layer, and a third layer having a high acoustic velocity relative to the first layer. The different acoustic velocities between the first and third layers cause relative shear displacements between the layers with the second layer damping the displacements between the first and third layers to reduce the table longitudinal vibration modes.

Gregory, Danny L. (Albuquerque, NM); Priddy, Tommy G. (Albuquerque, NM); Smallwood, David O. (Albuquerque, NM); Woodall, Tommy D. (Albuquerque, NM)

1991-01-01

324

Nanocrystal-Based Polymer Composites as Novel Functional Materials  

Microsoft Academic Search

\\u000a This chapter provides an overall picture of nanocrystal-polymer based composites and describes the key properties of these\\u000a original functional materials, particularly suited for advanced applications in photonic, optoelectronic as well as in sensing.\\u000a Here, we aim at pointing out the relevance of the incorporation of inorganic colloidal nanocrystals with size-dependent properties\\u000a in highly processable polymers. Due to the countless different

M. Striccoli; M. L. Curri; R. Comparelli

325

Manganese oxide–carbon composite as supercapacitor electrode materials  

Microsoft Academic Search

Nano-sized manganese oxide (Mn2O3) was incorporated homogeneously in templated mesoporous carbon to prepare Mn2O3–carbon nanocomposites, which were used as supercapacitor electrodes. Cyclic voltammetry was employed to investigate the electrochemical properties of the composite materials in an aqueous electrolyte under different scan rates. Results showed that templated mesoporous carbon with layered graphene domains holds a great promise for high-rate supercapacitor applications.

Li Li Zhang; Tianxin Wei; Wenjuan Wang; X. S. Zhao

2009-01-01

326

3D vector magnetic properties of soft magnetic composite material  

Microsoft Academic Search

Even under one-dimensional (1D) alternating or 2D rotating magnetic excitation, a magnetic material shows 3D magnetic property due to the rotation of magnetic domains. Only when the 3D properties are properly considered the understanding and modelling of the magnetisation process can be complete. This paper summarises our work about the investigation on the magnetic properties of soft magnetic composite (SMC)

Y. G. Guo; J. G. Zhu; Z. W. Lin; J. J. Zhong

2006-01-01

327

Aluminum Foam-Phase Change Material Composites as Heat Exchangers  

Microsoft Academic Search

The effects of geometric parameters of open-cell aluminum foams on the performance of aluminum foam-phase change material (PCM) composites as heat sinks are investigated by experiments. Three types of open-cell aluminum 6061 foams with similar relative densities and different cell sizes are used. Paraffin is selected as the PCM due to its excellent thermal stability and ease of handling. The

Sung-tae Hong; Darrell R. Herling

2007-01-01

328

Composite Materials for Marine Applications: Key Challenges for the Future  

Microsoft Academic Search

\\u000a This chapter presents the key challenges for the future use of composite materials for marine applications. Five technical\\u000a challenges have been identified: load transfer mechanisms, safety, life cycle assessment, concurrent engineering and structural\\u000a health monitoring. These are discussed in the following sections of the chapter. The mechanical behaviour of layered orthotropic\\u000a structures is considered for both adhesively bonded and hybrid

R. A. Shenoi; J. M. Dulieu-Barton; S. Quinn; J. I. R. Blake; S. W. Boyd

329

SRM nozzle design breakthroughs with advanced composite materials  

NASA Astrophysics Data System (ADS)

The weight reduction-related performance and cost of the Space Shuttle's Solid Rocket Motor (SRM) units' critical nozzle components are undergoing revolutionary improvements through the use of 3D-woven carbon/carbon and carbon/alumina composite materials. These can be used to fabricate the SRM's nozzle throat nondegradable insulators, thermostructural insulator, and exit cones. Additional developments are noted among nozzle-related structural components for additional rocket propulsion systems, including a three-piece extendible nozzle.

Berdoyes, Michel

1993-06-01

330

Optimized material composition to improve the physical and mechanical properties of extruded wood–plastic composites (WPCs)  

Microsoft Academic Search

Wood–plastic composite (WPC) is an environmentally progress way of combining recycled plastics and wood flour. The composite typically consists of four major elements: wood flour, thermoplastic plastics, coupling agent, and lubricant. The physical and mechanical properties of WPCs highly depend on the material formulation, and the optimal material composition is an essential topic of current research. This study investigated the

Shao-Yuan Leu; Tsu-Hsien Yang; Sheng-Fong Lo; Te-Hsin Yang

331

The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials  

NASA Technical Reports Server (NTRS)

During the past three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. As part of my startup package I received funds to construct a state-of-the-art experimental facility to study gas-solid reaction kinetics. Much of our effort was spent developing the methodology to measure the abundance and isotopic composition of Hg at ultratrace levels in solid materials. In our first study, the abundance and isotopic composition of Hg was determined in bulk samples of the Murchison (CM) and Allende (CV) carbonaceous chondrites. We have continued our study of mercury in primitive meteorites and expanded the suite of meteorites to include other members of the CM and CV chondrite group as well as CI and CO chondrites. Samples of the CI chondrite Orgueil, the CM chondrites Murray, Nogoya, and Cold Bokkeveld, the CO chondrites Kainsaz, Omans, and Isna, and the CV chondrites Vigarano, Mokoia, and Grosnaja were tested. We have developed a thermal analysis ICP-MS technique and applied it to the study of a suite of thermally labile elements (Zn, As, Se, Cd, In, Sn, Sb, Te, Hg, Au, Tl, Pb, and Bi) in geologic materials as well.

Lauretta, D. S.

2004-01-01

332

Autonomic composite hydrogels by reactive printing: materials and oscillatory response.  

PubMed

Autonomic materials are those that automatically respond to a change in environmental conditions, such as temperature or chemical composition. While such materials hold incredible potential for a wide range of uses, their implementation is limited by the small number of fully-developed material systems. To broaden the number of available systems, we have developed a post-functionalization technique where a reactive Ru catalyst ink is printed onto a non-responsive polymer substrate. Using a succinimide-amine coupling reaction, patterns are printed onto co-polymer or biomacromolecular films containing primary amine functionality, such as polyacrylamide (PAAm) or poly-N-isopropyl acrylamide (PNIPAAm) copolymerized with poly-N-(3-Aminopropyl)methacrylamide (PAPMAAm). When the films are placed in the Belousov-Zhabotinsky (BZ) solution medium, the reaction takes place only inside the printed nodes. In comparison to alternative BZ systems, where Ru-containing monomers are copolymerized with base monomers, reactive printing provides facile tuning of a range of hydrogel compositions, as well as enabling the formation of mechanically robust composite monoliths. The autonomic response of the printed nodes is similar for all matrices in the BZ solution concentrations examined, where the period of oscillation decreases in response to increasing sodium bromate or nitric acid concentration. A temperature increase reduces the period of oscillations and temperature gradients are shown to function as pace-makers, dictating the direction of the autonomic response (chemical waves). PMID:24651297

Kramb, R C; Buskohl, P R; Slone, C; Smith, M L; Vaia, R A

2014-03-01

333

Material Issues in Space Shuttle Composite Overwrapped Pressure Vessels  

NASA Technical Reports Server (NTRS)

Composite Overwrapped Pressure Vessels (COPV) store gases used in four subsystems for NASA's Space Shuttle Fleet. While there are 24 COPV on each Orbiter ranging in size from 19-40", stress rupture failure of a pressurized Orbiter COPV on the ground or in flight is a catastrophic hazard and would likely lead to significant damage/loss of vehicle and/or life and is categorized as a Crit 1 failure. These vessels were manufactured during the late 1970's and into the early 1980's using Titanium liners, Kevlar 49 fiber, epoxy matrix resin, and polyurethane coating. The COPVs are pressurized periodically to 3-5ksi and therefore experience significant strain in the composite overwrap. Similar composite vessels were developed in a variety of DOE Programs (primarily at Lawrence Livermore National Laboratories or LLNL), as well as for NASA Space Shuttle Fleet Leader COPV program. The NASA Engineering Safety Center (NESC) formed an Independent Technical Assessment (ITA) team whose primary focus was to investigate whether or not enough composite life remained in the Shuttle COPV in order to provide a strategic rationale for continued COPV use aboard the Space Shuttle Fleet with the existing 25-year-old vessels. Several material science issues were examined and will be discussed in this presentation including morphological changes to Kevlar 49 fiber under stress, manufacturing changes in Kevlar 49 and their effect on morphology and tensile strength, epoxy resin strain, composite creep, degradation of polyurethane coatings, and Titanium yield characteristics.

Sutter, James K.; Jensen, Brian J.; Gates, Thomas S.; Morgan, Roger J.; Thesken, John C.; Phoenix, S. Leigh

2006-01-01

334

Central Appalachian basin natural gas database: distribution, composition, and origin of natural gases  

USGS Publications Warehouse

The U.S. Geological Survey (USGS) has compiled a database consisting of three worksheets of central Appalachian basin natural gas analyses and isotopic compositions from published and unpublished sources of 1,282 gas samples from Kentucky, Maryland, New York, Ohio, Pennsylvania, Tennessee, Virginia, and West Virginia. The database includes field and reservoir names, well and State identification number, selected geologic reservoir properties, and the composition of natural gases (methane; ethane; propane; butane, iso-butane [i-butane]; normal butane [n-butane]; iso-pentane [i-pentane]; normal pentane [n-pentane]; cyclohexane, and hexanes). In the first worksheet, location and American Petroleum Institute (API) numbers from public or published sources are provided for 1,231 of the 1,282 gas samples. A second worksheet of 186 gas samples was compiled from published sources and augmented with public location information and contains carbon, hydrogen, and nitrogen isotopic measurements of natural gas. The third worksheet is a key for all abbreviations in the database. The database can be used to better constrain the stratigraphic distribution, composition, and origin of natural gas in the central Appalachian basin.

Roman-Colon, Yomayra A.; Ruppert, Leslie F.

2015-01-01

335

Natural-fiber-reinforced polymer composites in automotive applications  

NASA Astrophysics Data System (ADS)

In the past decade, natural-fiber composites with thermoplastic and thermoset matrices have been embraced by European car manufacturers and suppliers for door panels, seat backs, headliners, package trays, dashboards, and interior parts. Natural fibers such as kenaf, hemp, flax, jute, and sisal offer such benefits as reductions in weight, cost, and CO2, less reliance on foreign oil sources, and recyclability. However, several major technical considerations must be addressed before the engineering, scientific, and commercial communities gain the confidence to enable wide-scale acceptance, particularly in exterior parts where a Class A surface finish is required. Challenges include the homogenization of the fiber's properties and a full understanding of the degree of polymerization and crystallization, adhesion between the fiber and matrix, moisture repellence, and flame-retardant properties, to name but a few.

Holbery, James; Houston, Dan

2006-11-01

336

Solar-wind interactions - Nature and composition of lunar atmosphere  

NASA Technical Reports Server (NTRS)

The nature and composition of the lunar atmosphere are examined on the basis of solar-wind interactions, and the nature of the species in the trapped-gas layer is discussed using results of theoretical and experimental investigations. It is shown that the moon has a highly tenuous atmosphere consisting of various species derived from five sources: solar-wind interaction products, cosmic-ray interaction products, effects of meteoritic impacts, planetary degassing, and radioactive-decay products. Atmospheric concentrations are determined for those species derived from solar-wind protons, alpha particles, and oxygen ions. Carbon chemistry is briefly discussed, and difficulties encountered in attempts to determine quantitatively the concentrations of molecular oxygen, atomic oxygen, carbon monoxide, carbon dioxide, and methane are noted. The calculated concentrations are shown to be in good agreement with observations by the Apollo 17 lunar-surface mass spectrometer and orbital UV spectrometer.

Mukherjee, N. R.

1975-01-01

337

Determination of Residual Stress in Composite Materials Using Ultrasonic Waves  

NASA Technical Reports Server (NTRS)

The performance of high temperature composites can be significantly affected by the presence of residual stresses. These stresses arise during cooling processes from fabrication to room temperature due to mismatch of thermal expansion coefficients between matrix and fiber materials. This effect is especially pronounced in metal matrix and intermetallic composites. It can lead to plastic deformations, matrix cracking and fiber/matrix interface debonding. In this work the feasibility of ultrasonic techniques for residual stress assessment in composites is addressed. A novel technique for absolute stress determination in orthotropic materials from angular dependencies of ultrasonic velocities is described. The technique is applicable for determination of both applied and residual stresses and does not require calibration measurements on a reference sample. The important advantage of this method is that stress is determined simultaneously with stress-dependent elastic constants and is thus decoupled from the material texture. It is demonstrated that when the principal plane stress directions coincide with acoustical axes, the angular velocity data in the plane perpendicular to the stress plane may be used to determine both stress components. When the stress is off the acoustical axes, the shear and the difference of the normal stress components may be determined from the angular dependence of group velocities in the plane of stresses. Synthetic sets of experimental data corresponding to materials with different anisotropy and stress levels are used to check the applicability of the technique. The method is also verified experimentally. A high precision ultrasonic wave transmission technique is developed to measure angular dependence of ultrasonic velocities. Examples of stress determination from experimental velocity data are given. A method is presented for determination of velocities of ultrasonic waves propagating through the composite material with residual stresses. It is based on the generalized self-consistent multiple scattering model. Calculation results for longitudinal and shear ultrasonic wave velocities propagating perpendicular to the fibers direction in SCS-6/Ti composite with and without residual stresses are presented. They show that velocity changes due to presence of stresses are of order 1%.

Rokhlin, S. I.

1997-01-01

338

Determination of natural actinides and plutonium in marine particulate material  

Microsoft Academic Search

The natural actinides ²²⁷Ac, ²²⁸Th, ²³°Th, ²³²Th, ²³⁴Th, ²³¹Pa, ²³⁸U, and ²³⁴U and the ..cap alpha..-emitting plutonium isotopes are determined in samples of suspended marine particulate material and sediments. Analysis involves total dissolution of the samples to allow equilibration of the natural isotopes with added isotope yield monitors followed by coprecipitation of hydrolyzable metals at pH 7 with natural Fe

Robert F. Anderson; Alan P. Fleer

1982-01-01

339

Continuation of tailored composite structures of ordered staple thermoplastic material  

NASA Technical Reports Server (NTRS)

The search for the cost effective composite structure has motivated the investigation of several approaches to develop composite structure from innovative material forms. Among the promising approaches is the conversion of a planar sheet to components of complex curvature through sheet forming or stretch forming. In both cases, the potential for material stretch in the fiber direction appears to offer a clear advantage in formability over continuous fiber systems. A framework was established which allows the simulation of the anisotropic mechanisms of deformation of long discontinuous fiber laminates wherein the matrix phase is a viscous fluid. Predictions for the effective viscosities of a hyper-anisotropic medium consisting of collimated, discontinuous fibers suspended in viscous matrix were extended to capture the characteristics of typical polymers including non-Newtonian behavior and temperature dependence. In addition, the influence of fiber misorientation was also modeled by compliance averaging to determine ensemble properties for a given orientation distribution. A design tool is presented for predicting the effect of material heterogeneity on the performance of curved composite beams such as those used in aircraft fuselage structures. Material heterogeneity can be induced during manufacturing processes such as sheet forming and stretch forming of thermoplastic composites. This heterogeneity can be introduced in the form of fiber realignment and spreading during the manufacturing process causing radial and tangential gradients in material properties. Two analysis procedures are used to solve the beam problems. The first method uses separate two-dimensional elasticity solutions for the stresses in the flange and web sections of the beam. The separate solutions are coupled by requiring that forces and displacements match section boundaries. The second method uses an approximate Rayleigh-Ritz technique to find the solutions for more complex beams. Analyses are performed for curved beams of various cross-sections loaded in pure bending and with a uniform distributed load. Preliminary results show that the geometry of the beam dictates the effect of heterogeneity on performance. The role of heterogeneity is larger in beams with a small average radius-to-depth ration, R/t, where R is the average radius of the beam and t is the difference between the inside and outside radii. Results of the anlysis are in the form of stresses and displacements and are compared to both mechanics of materials and numerical solutions obtained using finite element analysis.

Santare, Michael H.; Pipes, R. Byron

1992-01-01

340

An enhanced Whipple Bumper system - Impact resistance of composite materials  

NASA Technical Reports Server (NTRS)

For long-duration space flights where human occupation is expected, micrometeroid and debris shields are necessary to prevent puncture of the pressure vessels. Current 'Whipple Bumper' designs range from single thin sheets of aluminum to complicated structures of many energy absorbing layers. This paper details the results of an experimental program tao determine the increased protection afforded by intermediate bumpers made of composite material structures. Various configurations of honeycomb support structures sandwiched between layers of materials such as Kevlar, Spectra, aluminum, and others are inserted between the bumper and pressure shell. The areal densities of each new material structure are maintained constant so that the results compare directly with single-sheet aluminum intermediate bumpers.

Zwiener, J.; Mount, A.; Herren, K.; Nettles, A.; Semmel, C.; Sims, J.

1992-01-01

341

Effective thermal conductivity of polycapillary composite materials. II. The influence of convective heat exchange in the channels on the effective thermal conductivity of polycapillary composite materials  

Microsoft Academic Search

In the preceding article [1], an analytical relationship making it possible to determine the effective transverse thermal conductivity X.y of polycapillary composite materials was obtained. This relationship establishes the relationship between Xy, the volumetric concentration and thermal conductivity of the components of a polycapillary composite material, and the geometric parameters of the structure of the material. In deriving the equation,

L. I. Tuchinskii; E. M. Veksler

1992-01-01

342

Natural radioactivity in common building construction and radiation shielding materials  

Microsoft Academic Search

Commonly used building construction materials, radiation shielding bricks, hematite aggregate and other materials have been analyzed for the activity concentration of the natural radionuclides, namely 238U, 232Th and 40K, besides the radon exhalation rates. The activity concentration for 238U, 232Th and 40K varies from 29±1 to 98±4Bqkg?1, 20±2 to 112±2.8Bqkg?1, and 200±8 to 1908±15.6Bqkg?1, respectively, in various materials studied in

R. G. Sonkawade; K. Kant; S. Muralithar; R. Kumar; R. C. Ramola

2008-01-01

343

Manipulating DC currents with bilayer bulk natural materials.  

PubMed

A novel and general method for spatially manipulating DC currents has been proposed and experimentally verified by only using bilayer bulk natural conductive materials. Our approach shows distinctive advantages with respect to homogeneity, isotropy, and independence of complicated microfabrication techniques. Our design scheme can be readily extended to robust manipulations of magnetic fields, thermal heat, elastic mechanics, and matter waves. PMID:24643906

Han, Tiancheng; Ye, Huapeng; Luo, Yu; Yeo, Swee Ping; Teng, Jinghua; Zhang, Shuang; Qiu, Cheng-Wei

2014-06-01

344

Using Natural Materials for Educational Toys: Examples from Ghana.  

ERIC Educational Resources Information Center

Describes educational toys that are made from natural and readily available materials in Ghana. Directions and diagrams for the pawpaw-leaf horn, milk-tin helicopter, pen-top propeller, bow and arrow, spinning top, and feather helicopter are included. (DDR)

William, Musah; Preston, Christine

1998-01-01

345

Modeling Natural Space Ionizing Radiation Effects on External Materials  

NASA Technical Reports Server (NTRS)

Predicting the effective life of materials for space applications has become increasingly critical with the drive to reduce mission cost. Programs have considered many solutions to reduce launch costs including novel, low mass materials and thin thermal blankets to reduce spacecraft mass. Determining the long-term survivability of these materials before launch is critical for mission success. This presentation will describe an analysis performed on the outer layer of the passive thermal control blanket of the Hubble Space Telescope. This layer had degraded for unknown reasons during the mission, however ionizing radiation (IR) induced embrittlement was suspected. A methodology was developed which allowed direct comparison between the energy deposition of the natural environment and that of the laboratory generated environment. Commercial codes were used to predict the natural space IR environment model energy deposition in the material from both natural and laboratory IR sources, and design the most efficient test. Results were optimized for total and local energy deposition with an iterative spreadsheet. This method has been used successfully for several laboratory tests at the Marshall Space Flight Center. The study showed that the natural space IR environment, by itself, did not cause the premature degradation observed in the thermal blanket.

Alstatt, Richard L.; Edwards, David L.; Parker, Nelson C. (Technical Monitor)

2000-01-01

346

Natural mineral tetrahedrite as a direct source of thermoelectric materials.  

PubMed

We show that a simple powder processing procedure using natural mineral tetrahedrite, the most widespread sulfosalt on earth, provides a low cost, high throughput means of producing thermoelectric materials with high conversion efficiency. These earth-abundant thermoelectrics can open the door to many new and inexpensive power generation opportunities. PMID:23503421

Lu, Xu; Morelli, Donald T

2013-04-28

347

Evaluation of Natural Gas Pipeline Materials and Infrastructure for  

E-print Network

Evaluation of Natural Gas Pipeline Materials and Infrastructure for Hydrogen/Mixed Gas Service Retrofitting Existing NG Pipelines fro Hydrogen/Hythane Service New Pipeline Installation and ROW Lower South Carolina Electric and Gas University of South Carolina Praxair Hydrogen Pipeline Working Group

348

Noninteractive macroscopic reliability model for ceramic matrix composites with orthotropic material symmetry  

NASA Technical Reports Server (NTRS)

A macroscopic noninteractive reliability model for ceramic matrix composites is presented. The model is multiaxial and applicable to composites that can be characterized as orthotropic. Tensorial invariant theory is used to create an integrity basis with invariants that correspond to physical mechanisms related to fracture. This integrity basis is then used to construct a failure function per unit volume (or area) of material. It is assumed that the overall strength of the composite is governed by weakest link theory. This leads to a Weibull type model similar in nature to the principle of independent action (PIA) model for isotropic monolithic ceramics. An experimental program to obtain model parameters is briefly discussed. In addition, qualitative features of the model are illustrated by presenting reliability surfaces for various model parameters.

Duffy, Stephen F.; Manderscheid, Jane M.

1989-01-01

349

Compositions for enhancing hydroysis of cellulosic material by cellulolytic enzyme compositions  

DOEpatents

The present invention relates to compositions comprising a GH61 polypeptide having cellulolytic enhancing activity and an organic compound comprising a carboxylic acid moiety, a lactone moiety, a phenolic moiety, a flavonoid moiety, or a combination thereof, wherein the combination of the GH61 polypeptide having cellulolytic enhancing activity and the organic compound enhances hydrolysis of a cellulosic material by a cellulolytic enzyme compared to the GH61 polypeptide alone or the organic compound alone. The present invention also relates to methods of using the compositions.

Quinlan, Jason; Xu, Feng; Sweeney, Matthew; Johansen, Katja Salomon

2014-09-30

350

The use of natural materials in nanocarbon synthesis.  

PubMed

Nanomaterials are shifting from laboratory-scale preparation to industrial production. The energy costs and starting materials (feedstock, catalyst, and support) consumed or used in the mass production of nanomaterials are issues that limit their broad application. Natural materials, such as sand, rock, and lava, contain small or trace amounts of metals or metal oxides of nanometer-scale sizes and have been recently used as catalysts for the production of carbon nanotubes (CNTs), providing an interesting way to lower the production cost of CNTs. However, the sustainability of the whole production process still needs to be explored. Layered minerals (e.g., clays) are used to produce CNT-clay hybrids, which can be further used to synthesize polymer-CNT-clay nanocomposites. Natural materials and some byproducts of industrial production processes have been explored as carbon sources for nanocarbon synthesis. This Minireview highlights some recent promising work and prospects for the use of natural materials in the synthesis of CNTs, carbon nanofibers (CNFs), and nanocomposites, and their applications in catalysis and in materials science. PMID:19834932

Su, Dang Sheng

2009-01-01

351

Study of polypyrrole graphite composite as anode material for secondary lithium-ion batteries  

E-print Network

Study of polypyrrole graphite composite as anode material for secondary lithium-ion batteries of the composite. The composite material has been studied for specific discharge capacity, coulombic efficiency, rate capability and cycle life using a variety of electrochemical methods. The composite SFG10 graphite

Popov, Branko N.

352

Composite materials comprising two jonal functions and methods for making the same  

Microsoft Academic Search

The present invention generally relates to mechanisms for preventing undesirable oxidation (i.e., oxidation protection mechanisms) in composite bodies. The oxidation protection mechanisms include getterer materials which are added to the composite body which gather or scavenge undesirable oxidants which may enter the composite body. The getterer materials may be placed into at least a portion of the composite body such

Ali Syed Fareed; John Edward Garnier; Gerhard Hans Schiroky; Christopher Robin Kennedy; Birol Sonuparlak

2001-01-01

353

Digitally tunable physicochemical coding of material composition and topography in continuous microfibres  

NASA Astrophysics Data System (ADS)

Heterotypic functional materials with compositional and topographical properties that vary spatiotemporally on the micro- or nanoscale are common in nature. However, fabricating such complex materials in the laboratory remains challenging. Here we describe a method to continuously create microfibres with tunable morphological, structural and chemical features using a microfluidic system consisting of a digital, programmable flow control that mimics the silk-spinning process of spiders. With this method we fabricated hydrogel microfibres coded with varying chemical composition and topography along the fibre, including gas micro-bubbles as well as nanoporous spindle-knots and joints that enabled directional water collection. We also explored the potential use of the coded microfibres for tissue engineering applications by creating multifunctional microfibres with a spatially controlled co-culture of encapsulated cells.

Kang, Edward; Jeong, Gi Seok; Choi, Yoon Young; Lee, Kwang Ho; Khademhosseini, Ali; Lee, Sang-Hoon

2011-11-01

354

Thermal cum DC Camouflage in Duet with Undecorated Natural Materials  

E-print Network

To manipulate various types of physical signals in one single device has long captivated the attention of scientists and engineers. This however is very challenging, if not impossible, even for emerging metamaterials. Up to date, many artificial materials have been proposed, theoretically and (or) experimentally, for manipulating various waves/signals on a one-function-one-device basis. In this work, for the very first time, we employ undecorated natural materials to experimentally demonstrate a simultaneous camouflage for thermal current and electric dc current on the same device. It demonstrates how ingenuity can overcome the limitations of natural material systems without the need for complex decoration to impart inhomogeneous and (or) anisotropic properties, which was previously considered impossible to accomplish except by using metamaterials.

Yang, Tian-Zhi; Gao, Dongliang; Wu, Linzhi; Li, Baowen; Thong, John T L; Qiu, Cheng-Wei

2015-01-01

355

Composite material shear property measurement using the Iosipescu specimen  

NASA Technical Reports Server (NTRS)

A detailed evaluation of the suitability of the Iosipescu specimen tested in the modified Wyoming fixture is presented. Finite element analysis and moire interferometry are used to assess the uniformity of the shear stress field in the test section of unidirectional and cross-ply graphite-epoxy composites. The nonuniformity of the strain field and the sensitivity of some fiber orientations to the specimen/fixture contact mechanics are discussed. The shear responses obtained for unidirectional and cross-ply graphite-epoxy composites are discussed and problems associated with anomalous behavior are addressed. An experimental determination of the shear response of a range of material systems using strain gage instrumentation and moire interferometry is performed.

Ho, Henjen; Budiman, Haryanto T.; Tsai, Ming-Yi; Morton, John; Farley, Gary L.

1992-01-01

356

Tuneable broadband optical filter based on soft-composite materials  

NASA Astrophysics Data System (ADS)

We report on the realization and characterization of a ‘free space’ diffractive optical filter based on a periodic structure realized in soft composite materials. By combining a high stability optical holographic setup with a light sensitive composite mixture, we have realized a structure made of polymeric slices alternated to pure, well aligned, nematic liquid crystals. Its polarization dependent diffractive properties have been exploited for realizing a diffractive, band-gap based, broadband optical filter. The sample is characterized in terms of its morphological, optical and electro-optical properties. We show that both electric fields and temperature variations can be exploited to tune the position of the diffractive band-gap of about 83 nm and 116 nm respectively.

De Sio, Luciano; Caligiuri, Vincenzo; Umeton, Cesare

2014-06-01

357

Recycling By Solvolysis Thermosetting Composite Materials Of Sustainable Surface Transport  

SciTech Connect

A solvolysis process is studied to degrade an unsaturated polyester resin based on DCPD (dicyclopentadiene) and crosslinked with styrene, as the matrix of a composite material reinforced with long glass fibers. The study presented here investigates in particular the hydrolysis in conditions below the critical point of water (T<374 deg. C and P<221bar) in a batch reactor. Process window and parameter influences were studied by a Design of Experiments (DOE) approach (1). A tar-like substance issued from thermal degradations is formed in greater or lesser quantities depending on the operating conditions, and coats the fibers. The appearance of the composite samples and the degree of conversion for the degradation at 250 deg. C lead us to make a parallel with osmosis phenomena to explain the initiation mechanism of the degradation.

Oliveux, Geraldine; Le Gal La Salle, Eric [Laboratoire de Thermocinetique de Nantes (LTN), UMR CNRS 6607, Ecole Polytechnique de l'Universite de Nantes, Rue Christian Pauc, 44303 Nantes (France); Bailleul, Jean-Luc [Laboratoire Energetique, Mecanique et Materiaux(LE2M) de l'Institut Catholique des Arts et Metiers de Nantes, 35 avenue du champ de Manoeuvres, 44470 Carquefou (France)

2011-01-17

358

Super-hybrid composites - An emerging structural material  

NASA Technical Reports Server (NTRS)

Specimens of super-hybrids and advanced fiber composites were subjected to extensive tests to determine their mechanical properties, including impact and thermal fatigue. The super-hybrids were fabricated by a procedure similar to that reported by Chamis et al., (1975). Super-hybrids subjected to 1000 cycles of thermal fatigue from -100 to 300 F retained over 90% of their longitudinal flexural strength and over 75% of their transverse flexural strength; their transverse flexural strength may be as high as 8 times that of a commercially supplied boron/1100-Al composite. The thin specimen Izod longitudinal impact resistance of the super-hybrids was twice that of the boron/110-Al material. Super-hybrids subjected to transverse tensile loads exhibited nonlinear stress-strain relationships. The experimentally determined initial membrane (in-plane) and bending elastic properties of super-hybrids were predicted adequately by linear laminate analysis.

Chamis, C. C.; Lark, R. F.; Sullivan, T. L.

1975-01-01

359

Recycling By Solvolysis Thermosetting Composite Materials Of Sustainable Surface Transport  

NASA Astrophysics Data System (ADS)

A solvolysis process is studied to degrade an unsaturated polyester resin based on DCPD (dicyclopentadiene) and crosslinked with styrene, as the matrix of a composite material reinforced with long glass fibers. The study presented here investigates in particular the hydrolysis in conditions below the critical point of water (T<374° C and P<221bar) in a batch reactor. Process window and parameter influences were studied by a Design of Experiments (DOE) approach (1). A tar-like substance issued from thermal degradations is formed in greater or lesser quantities depending on the operating conditions, and coats the fibers. The appearance of the composite samples and the degree of conversion for the degradation at 250° C lead us to make a parallel with osmosis phenomena to explain the initiation mechanism of the degradation.

Oliveux, Géraldine; Le Gal La Salle, Eric; Bailleul, Jean-Luc

2011-01-01

360

Finite element analysis of composites materials for aerospace applications  

NASA Astrophysics Data System (ADS)

Composites materials are intended to be used more extensively as an alternative of aluminum structure in aircraft and aerospace applications. This is due to their attractive properties as high strength-to-weight ratio and stiffness-to-weight ratio. Besides that it clarifies the growing interest for composites materials due to advantages of lightweight, high strength, high stiffness, superior fatigue life, tremendous corrosion resistance and low cost manufacturing. In this study, a finite element analysis (FEA) of fiberglass unidirectional E-type was analyzed in the framework of ABAQUS finite element commercial software. The analysis was done to quantify the mechanical properties and response of unidirectional E-glass in term of tensile, compression and thermal responses. From the analysis, the maximum and minimum values of stress and strain for E-glass 21xK43 Gevetex and Silenka E-glass 1200tex were obtained and stress-strain curve is presented. The ultimate load of failure, elastic behavior, tensile strength and other properties for each laminated plates under tensile and thermal-stress are determined from stress-strain curves. The simulation will run twice for each material where the first simulation based on orientation angles of 45° for ply-1, -45° for ply-2 and 90° for ply-3 while the second simulation, the orientation angles is 0° for all plies. The simulation is successfully conducted and verified by experimental data.

Nurhaniza, M.; Ariffin, M. K. A.; Ali, Aidy; Mustapha, F.; Noraini, A. W.

2010-05-01

361

Physics in ``Polymers, Composites, and Sports Materials" an Interdisciplinary Course  

NASA Astrophysics Data System (ADS)

The undergraduate science course described uses the themes of polymers and composites, as used in sports materials, to teach some key concepts in introductory chemistry and physics. The course is geared towards students who are interested in science, but are still completing prerequisite mathematics courses required for science majors. Each class is built around a laboratory activity. Atoms, molecules and chemical reactions are taught in reference to making polyvinyl acetate (white glue) and polyvinyl alcohol (gel glue). These materials, combined with borax, form balls which are subsequently used in physics activities centered on free-fall and the coefficient of restitution. These activities allow the introduction of kinematics and dynamics. A free fall activity involving ice pellets, with and without embedded tissue paper, illustrates the properties of composites. The final series of activities uses balls, shoes, racquets and bats to further illustrate dynamics concepts (including friction, momentum and energy). The physical properties of these sports objects are discussed in terms of the materials of which they are made. The evaluation plan to determine the effectiveness of these activities and preliminary results are also presented.

Hagedorn, Eric; Suskavcevic, Milijana

2007-10-01

362

Present and Future Automotive Composite Materials Research Efforts at DOE  

SciTech Connect

Automobiles of the future will be forced to travel fi.uther on a tank of fuel while discharging lower levels of pollutants. Currently, the United States uses in excess of 16.4 million barrels of petroleum per day. Sixty-six percent of that petroleum is used in the transportation of people and goods. Automobiles currently account for just under two-thirds of the nation's gasoline consumptio~ and about one-third of the total United States energy usage. [1] By improving transportation related fiel efficiency, the United States can lessen the impact that emissions have on our environment and provide a cleaner environment for fiture generations. In 1992, The Department of Energy's (DOE) Office of Transportation Materials completed a comprehensive program plan entitled, The Lightweight MateriaIs (LWko Multi-Year Program Plan, for the development of technologies aimed at reducing vehicle mass [2]. This plan was followed in 1997 by the more comprehensive Office of Advanced Automotive Technologies research and development plan titled, Energy Eficient Vehicles for a Cleaner Environment [3] which outlines the department's plans for developing more efficient vehicles during the next ~een years. Both plans identi~ potential applications, technology needs, and R&D priorities. The goal of the Lightweight Materials Program is to develop materials and primary processing methods for the fabrication of lighter weight components which can be incorporated into automotive systems. These technologies are intended to reduce vehicle weight, increase fuel efficiency and decrease emissions. The Lightweight Materials program is jointly managed by the Department of Energy(DOE) and the United States Automotive Materials Partnership (USAMP). Composite materiak program work is coordinated by cooperative research efforts between the DOE and the Automotive Composites Consortium (ACC).

Warren, C.D.

1999-07-03

363

Parameterization of structures in HE composites using surrogate materials: A small angle neutron scattering investigation  

SciTech Connect

High explosive materials used in the nuclear stockpile are composites of crystalline high explosives (HE) with binder materials, such as Estane. In such materials, there are naturally occurring density fluctuations (defects) due to cracks, internal (in the HE) and external (in the binder) voids and other artifacts of preparation. Changes in such defects due to material aging can affect the response of explosives due to shock, impact and thermal loading. Modeling efforts are attempting to provide quantitative descriptions of explosive response from the lowest ignition thresholds to the development of full blown detonations and explosions, however, adequate descriptions of these processes require accurate measurements of a number of structural parameters of the HE composite. Since different defects are believed to affect explosive sensitivity in different ways it is necessary to quantitatively differentiate between defect types. The authors report here preliminary results of SANS measurements on surrogates for HE materials. The objective of these measurements was to develop methodologies using SANS techniques to parameterize internal void size distributions in a surrogate material, sugar, to simulate an HE used in the stockpile, HMX. Sugar is a natural choice as a surrogate material, as it has the same crystal structure, has similar intragranular voids and has similar mechanical properties as HMX. It is used extensively as a mock material for explosives. Samples were used with two void size distributions: one with a sufficiently small mean particle size that only small occluded voids are present in significant concentrations, and one where the void sizes could be larger. By using methods in small-angle neutron scattering, they were able to isolate the scattering arising from particle-liquid interfaces and internal voids.

Mang, J.T.; Hjelm, R.P.; Skidmore, C.B.; Howe, P.M.

1996-07-01

364

Dynamic permeability in soft magnetic composite materials A. Chevalier and M. Le Floc'ha)  

E-print Network

Dynamic permeability in soft magnetic composite materials A. Chevalier and M. Le Floc on microwave ap- plications of composite materials consisting of soft magnetic particles embedded in insulating, the ability of the model to predict the dynamic properties of many composite magnetic materials

Paris-Sud XI, Université de

365

Characterization and the Pattern of Surfaces of Sealant with nano size Composite Materials  

NASA Astrophysics Data System (ADS)

Nano composite sealant is low viscosity, room temperature cured, opaque and flowable nature. They have variety of uses such as potting, pressure sealant and shock resistant. Most important factor influencing use of fillers in polymer composites is their ability to effectively transfer the applied load in the matrix. The effective utilization of fillers in composites for structural applications depends strongly on the ability to disperse the nano fillers homogeneously in the matrix without damaging them. R-Belite supper epoxy adhesive (RBSEA) were formulated with different nano fillers (KCl, Al2O3, ZrO2, SiO2, ZrO2) at room temperature. The composite were prepared with the 0.02 to 0.10 weight ratios to promote the nucleation of the nanoparticles in the applied sealant. Two main problems which arise in improving the properties are poor dispersion of the fillers in the composite and weak bonding between nano fillers and the matrix. These problems are solved by mechanical and chemical means. It was observed that mechanical properties like tensile strength, elongation hardness etc and thermal properties were also improved with incorporation of nanofillers in the working applied polymer matrix. The dispersion of nano fillers in polymer matrix is studied by Scanning electron microscopy (SEM). The results confirm the presence of nanomaterial in RBSEA/fillers nanocomposites. SEM is also used to characterize the pattern of surfaces with nano size composite materials.

Quddos, A.; Samtio, N. H.; Syed, A. M.

2013-06-01

366

Task 5.9 - use of coal ash in recycled plastics and composite materials  

SciTech Connect

The goal of this research project by the Energy & Environmental Research Center (EERC) was to determine the potential for coal ash to serve as a {open_quote}functional filler{close_quotes} in plastics and other composite materials, with special emphasis on recycled plastics. The term functional filler is intended to indicate that the material added to the plastic does more than take up space and extend the use of the polymer. Determining the functional filler potential of ash was not the only intent of this project, since another prime objective was to find a use for materials currently considered waste. The term functional filler also opened a door to the use of cenospheres, which are currently marketed and for which there is sufficient market demand that they do not fit the category of a waste even though they are a product of coal combustion. Cenospheres, hollow spherical ash particles, were selected because of their unique properties. Although they currently have commercial applications, the unique nature of these materials make them an excellent candidate for use as a functional filler in composites. The ability to produce a commercially viable product from waste streams and a recycled material is a positive step toward reducing solid waste. The first task, since there are numerous types of coal ash, was to select suitable ash types for use in this project. Three basic types of material were selected: fly ash, a bottom ash, and a unique form of coal ash known as cenospheres.

Hassett, D.J.; Dockter, B.A.; Eylands, K.E.; Pflughoeft-Hassett, D.F.

1995-07-01

367

Task 5.9 use of coal ash in recycled plastics and composite materials. Topical report  

SciTech Connect

The goal of this research project by the Energy & Environmental Research Center (EERC) was to determine the potential for coal ash to serve as a {open_quotes}functional filler{close_quotes} in plastics and other composite materials, with special emphasis on recycled plastics. The term functional filler is intended to indicate that the material added to the plastic does more than take up space and extend the use of the polymer. Determining the functional filler potential of ash was not the only intent of this project, since another prime objective was to find a use for materials currently considered waste. The term functional filler also opened a door to the use of cenospheres, which are currently marketed and for which there is sufficient market demand that they do not fit the category of a waste even though they are a product of coal combustion. Cenospheres, hollow spherical ash particles, were selected because of their unique properties. Although they currently have commercial applications, the unique nature of these materials make them an excellent candidate for use as a functional filler in composites. The ability to produce a commercially viable product from waste streams and a recycled material is a positive step toward reducing solid waste. The first task, since there are numerous types of coal ash, was to select suitable ash types for use in this project. Three basic types of material were selected: fly ash, a bottom ash, and a unique form of coal ash known as cenospheres.

Hassett, D.J.; Dockter, B.A.; Eylands, K.E.; Pflughoeft-Hassett, D.F.

1995-11-01

368

Task 6.7.3 - Interfacial Mass Transport Effects in Composite Materials  

SciTech Connect

Advanced metal-matrix composites (MMCS) consisting of titanium-based alloys possess some unique mechanical, physical, and chemical characteristics that make them highly desirable for aircraft and gas turbine engines. Tailoring MMC properties is essential for advanced product design in materials processing. The main factors that affect materials processing and, further, the nature of a metal-ceramic interface, its structure, and morphological stability is liquid surface mass transport related to adhesional wetting physical effect) and reactive wetting (chemical effect). Surfaces and interfaces dominate many of the technologically important processes in composite materials such as liquid-solid sintering and joining. The objective of this work is threefold: 1) to get insight into the role of the nonstoichiometry of chemical composition in ceramic materials used as reinforcement components in MMC processing, 2) to extend previous energetic analysis of mass transport phenomena to wetting behavior between liquid metal and the quasi-solid like skin resulting from the presolidification of liquid on nonstoichiometric solids on a scale of interatomic distance, and 3) to provide experimental verification of our concept.

Jan W. Nowok

1998-02-01

369

Task 6.7.3 - Interfacial Mass Transport Effects in Composite Materials  

SciTech Connect

Advanced metal-matrix composites (MMCS) consisting of titanium-based alloys possess some unique mechanical, physical, and chemical characteristics that make them highly desirable for aircraft and gas turbine engines. Tailoring MMC properties is essential for advanced product design in materials processing. The main factors that affect materials processing and, further, the nature of a metal-ceramic interface, its structure, and morphological stability is liquid surface mass transport related to adhesional wetting (physical effect) and reactive wetting (chemical effect).' Surfaces and interfaces dominate many of the technologically important processes in composite materials such as liquid-solid sintering and joining. The objective of this work is threefold: 1) to get insight into the role of the nonstoichiometry of chemical composition in ceramic materials used as reinforcement components in MMC processing, 2) to extend previous energetic analysis of mass transport phenomena to wetting behavior between liquid metal and the quasi-solidlike skin resulting from the presolidification of liquid on nonstoichiometric solids on a scale of interatomic distance, and 3) to provide experimental verification of our concept.

Jan W. Nowok

1998-02-01

370

Compressive strength after blast of sandwich composite materials.  

PubMed

Composite sandwich materials have yet to be widely adopted in the construction of naval vessels despite their excellent strength-to-weight ratio and low radar return. One barrier to their wider use is our limited understanding of their performance when subjected to air blast. This paper focuses on this problem and specifically the strength remaining after damage caused during an explosion. Carbon-fibre-reinforced polymer (CFRP) composite skins on a styrene-acrylonitrile (SAN) polymer closed-cell foam core are the primary composite system evaluated. Glass-fibre-reinforced polymer (GFRP) composite skins were also included for comparison in a comparable sandwich configuration. Full-scale blast experiments were conducted, where 1.6×1.3?m sized panels were subjected to blast of a Hopkinson-Cranz scaled distance of 3.02?m?kg(-1/3), 100?kg TNT equivalent at a stand-off distance of 14?m. This explosive blast represents a surface blast threat, where the shockwave propagates in air towards the naval vessel. Hopkinson was the first to investigate the characteristics of this explosive air-blast pulse (Hopkinson 1948 Proc. R. Soc. Lond. A 89, 411-413 (doi:10.1098/rspa.1914.0008)). Further analysis is provided on the performance of the CFRP sandwich panel relative to the GFRP sandwich panel when subjected to blast loading through use of high-speed speckle strain mapping. After the blast events, the residual compressive load-bearing capacity is investigated experimentally, using appropriate loading conditions that an in-service vessel may have to sustain. Residual strength testing is well established for post-impact ballistic assessment, but there has been less research performed on the residual strength of sandwich composites after blast. PMID:24711494

Arora, H; Kelly, M; Worley, A; Del Linz, P; Fergusson, A; Hooper, P A; Dear, J P

2014-05-13

371

Multi scale analysis by acoustic emission of damage mechanisms in natural fibre woven fabrics/epoxy composites.  

NASA Astrophysics Data System (ADS)

This paper proposes to develop an experimental program to characterize the type and the development of damage in composite with complex microstructure. A multi-scale analysis by acoustic emission has been developed and applied to hemp fibre woven fabrics/epoxy composite. The experimental program consists of tensile tests performed on single yarn, neat epoxy resin and composite materials to identify their AE amplitude signatures. A statistical analysis of AE amplitude signals has been realised and correlated with microscopic observations. Results have enabled to identify three types of damage in composites and their associated AE amplitudes: matrix cracking, interfacial debonding and reinforcement damage and fracture. Tracking of these damage mechanisms in hemp/epoxy composites has been performed to show the process of damage development in natural fibre reinforced composites.

Bonnafous, C.; Touchard, F.; Chocinski-Arnault, L.

2010-06-01

372

Composite slip table of dissimilar materials for damping longitudinal modes  

DOEpatents

A vibration slip table for use in a vibration testing apparatus is disclosed. The tables comprised of at least three composite layers of material; a first metal layer, a second damping layer, and a third layer having a high acoustic velocity relative to the first layer. The different acoustic velocities between the first and third layers cause relative shear displacements between the layers with the second layer damping the displacements between the first and third layers to reduce the table longitudinal vibration modes. 6 figures.

Gregory, D.L.; Priddy, T.G.; Smallwood, D.O.; Woodall, T.D.

1991-06-18

373

Collagen hydrolysate based collagen/hydroxyapatite composite materials  

NASA Astrophysics Data System (ADS)

The aim of this study was to study the influence of collagen hydrolysate (HAS) on the formation of ternary collagen-hydrolysate/hydroxyapatite composite materials (COLL-HAS/HA). During the precipitation process of HA, a large amount of brushite is resulted at pH = 7 but, practically pure HA is obtained at pH ? 8. The FTIR data reveal the duplication of the most important collagen absorption bands due to the presence of the collagen hydrolysate. The presence of collagen hydrolysate is beneficial for the management of bone and joint disorders such as osteoarthritis and osteoporosis.

Ficai, Anton; Albu, Madalina Georgiana; Birsan, Mihaela; Sonmez, Maria; Ficai, Denisa; Trandafir, Viorica; Andronescu, Ecaterina

2013-04-01

374

Pressure-reaction synthesis of titanium composite materials  

DOEpatents

A pressure-reaction synthesis process for producing increased stiffness and improved strength-to-weight ratio titanium metal matrix composite materials comprising exothermically reacting a titanium powder or titanium powder alloys with non-metal powders or gas selected from the group consisting of C, B, N, BN, B.sub.4 C, SiC and Si.sub.3 N.sub.4 at temperatures from about 900.degree. to about 1300.degree. C., for about 5 to about 30 minutes in a forming die under pressures of from about 1000 to 5000 psi.

Oden, Laurance L. (Albany, OR); Ochs, Thomas L. (Albany, OR); Turner, Paul C. (Albany, OR)

1993-01-01

375

Numerical analysis of the Iosipescu specimen for composite materials  

NASA Technical Reports Server (NTRS)

A finite element analysis of the Iosipescu shear tests for unidirectional and cross-ply composites is presented. It is shown that an iterative analysis procedure must be used to model the fixture-specimen kinematics. The correction factors which are needed to compensate for the nonuniformity of stress distribution in calculating shear modulus are shown to be dependent on the material orthotropic ratio and the finite element loading models. Test section strain distributions representative of typical graphite-epoxy specimens are also presented.

Ho, H.; Tsai, M. Y.; Morton, J.; Farley, G. L.

1993-01-01

376

Numerical analysis of the Iosipescu specimen for composite materials  

NASA Technical Reports Server (NTRS)

A finite element analysis of the Iosipescu shear tests for unidirectional and cross-ply composites is presented. It is shown that an iterative analysis procedure must be used to model the fixture-specimen kinematics. The correction factors which are needed to compensate for the nonuniformity of stress distribution in calculating shear modulus are shown to be dependent on the material orthotropic ratio and the finite element loading models. Test section strain distributions representative of typical graphite-epoxy specimens are also presented.

Ho, H.; Tsai, M. Y.; Morton, J.; Farley, G. L.

1992-01-01

377

Nonequilibrium material effects on the behavior of polymeric composite matrices and their related composites  

NASA Technical Reports Server (NTRS)

The effects of physical aging on the material properties of some linear and network macromolecular glasses are discussed. The free volume concept is used to describe this behavior. The effect of physical aging on properties of some uniaxial graphite/fiber epoxy resin composites is investigated using stress relaxation in both tensile and flexural modes. The matrix polymers used were resins both of which are based on a 4,4-methylenedianiline derivative of epichlorohydrin with diamino diphenyl sulfone (DDS) as the curing agent. The matrix resin, as used in the practical application in composites, not fully cured and the glass transition of the network was dependent on the curing schedule. The physical aging of the bulk crosslinked epoxy was found to depend on the annealing temperature, and the T sub g of the resin. The physical aging of the composite, monitored by the stress relaxation method, was found to be dependent on the testing direction.

Wilkes, G. L.

1982-01-01

378

Naturally Occurring Radioactive Materials in Cargo at US Borders  

SciTech Connect

In the U.S. and other countries, large numbers of vehicles pass through border crossings each day. The illicit movement of radioactive sources is a concern that has resulted in the installation of radiation detection and identification instruments at border crossing points. This activity is judged to be necessary because of the possibility of an act of terrorism involving a radioactive source that may include any number of dangerous radionuclides. The problem of detecting, identifying, and interdicting illicit radioactive sources is complicated by the fact that many materials present in cargo are somewhat radioactive. Some cargo contains naturally occurring radioactive material or technologically-enhanced naturally occurring radioactive material that may trigger radiation portal monitor alarms. Man-made radioactive sources, especially medical isotopes, are also frequently observed and produce alarms. Such nuisance alarms can be an operational limiting factor for screening of cargo at border crossings. Information about the nature of the radioactive materials in cargo that can interfere with the detection of radionuclides of concern is necessary. This paper provides such information for North American cargo, but the information may also be of use to border control officials in other countries. (PIET-43741-TM-361)

Kouzes, Richard T.; Ely, James H.; Evans, John C.; Hensley, Walter K.; Lepel, Elwood A.; McDonald, Joseph C.; Schweppe, John E.; Siciliano, Edward R.; Strom, Daniel J.; Woodring, Mitchell L.

2006-01-01

379

Investigation of composite materials property requirements for sonic fatigue research  

NASA Technical Reports Server (NTRS)

Experimental techniques for determining the extensional and bending stiffness characteristics for symmetric laminates are presented. Vibrational test techniques for determining the dynamic modulus and material damping are also discussed. Partial extensional stiffness results intially indicate that the laminate theory used for predicting stiffness is accurate. It is clearly shown that the laminate theory can only be as accurate as the physical characteristics describing the lamina, which may vary significantly. It is recommended that all of the stiffness characteristics in both extension and bending be experimentally determined to fully verify the laminate theory. Dynamic modulus should be experimentally evaluated to determine if static data adequately predicts dynamic behavior. Material damping should also be ascertained because laminate damping is an order of magnitude greater than found in common metals and can significantly effect the displacement response of composite panels.

Patrick, H. V. L.

1985-01-01

380

Mixed composition materials suitable for vacuum web sputter coating  

NASA Technical Reports Server (NTRS)

Ion beam sputter deposition techniques were used to investigate simultaneous sputter etching of two component targets so as to produce mixed composition films. Although sputter deposition has been largely confined to metals and metal oxides, at least one polymeric material, poly-tetra-fluorethylene, has been demonstrated to produce sputtered fragments which repolymerize upon deposition to produce a highly cross-linked fluoropolymer resembling that of the parent target Fluoropolymer-filled silicon dioxide and fluoropolymer-filled aluminum oxide coatings have been deposited by means of ion beam sputter coat deposition resulting in films having material properties suitable for aerospace and commercial applications. The addition of fluoropolymer to silicon dioxide films was found to increase the hydrophobicity of the resulting mixed films; however, adding fluoropolymer to aluminum oxide films resulted in a reduction in hydrophobicity, thought to be caused by aluminum fluoride formation.

Banks, Bruce A.; Rutledge, Sharon K.; Dever, Joyce A.; Bruckner, Eric J.; Walters, Patricia; Hambourger, Paul D.

1996-01-01

381

Environmental exposure effects on composite materials for commercial aircraft  

NASA Technical Reports Server (NTRS)

The effects of environmental exposure on composite materials are determined. The environments considered are representative of those experienced by commercial jet aircraft. Initial results have been compiled for the following material systems: T300/5208, T300/5209, and T300/934. Future results will include AS-1/3501-6 and Kevlar 49/F161-188. Specimens are exposed on the exterior and interior of 737 airplanes of three airlines, and to continuous ground-level exposure at four locations. In addition, specimens are exposed in the laboratory to conditions such as: simulated ground-air-ground, weatherometer, and moisture. Residual strength results are presented for specimens exposed for up to five years at five ground-level exposure locations and on airplanes from one airline.

Coggeshall, R. L.

1985-01-01

382

Selection of optimal composition-control parameters for friable materials  

SciTech Connect

A method for composition analysis of coal and minerals is proposed which uses scattered gamma radiation and does away with preliminary sample preparation to ensure homogeneous particle density, surface area, and size. Reduction of the error induced by material heterogeneity has previously been achieved by rotation of the control object during analysis. A further refinement is proposed which addresses the necessity that the contribution of the radiation scattered from each individual surface to the total intensity be the same. This is achieved by providing a constant linear rate of travel for the irradiated spot through back-and-forth motion of the sensor. An analytical expression is given for the laws of motion for the sensor and test tube which provides for uniform irradiated area movement along a path analogous to the Archimedes spiral. The relationships obtained permit optimization of measurement parameters in analyzing friable materials which are not uniform in grain size.

Pak, Yu.N.; Vdovkin, A.V.

1988-05-01

383

Composites  

NSDL National Science Digital Library

In this activity, learners explore how composites work by creating and testing their own composite for an imaginary company. This activity shows learners that composites are simply materials that are made up of two or more visibly distinct substances. Use this activity to talk about how composites are everywhere in our lives.

Research, Cornell C.

2003-01-01

384

Overview of naturally occurring Earth materials and human health concerns  

NASA Astrophysics Data System (ADS)

The biosphere and the Earth's critical zone have maintained a dynamic equilibrium for more than 3.5 billion years. Except for solar energy, almost all terrestrial substances necessary for life have been derived from near-surface portions of the land, hydrosphere, and atmosphere. If aggregate biological activities are less than the rate of nutrient supply and/or resource renewal, sustained population growth is possible. Where the replenishment rate of a life-sustaining Earth material is finite, usage may reach a condition of dynamic equilibrium in which biological consumption equals but on average cannot exceed the overall supply. Although large, most natural resources are present in finite abundances; for such commodities, excessive present-day human utilization reduces future availability, and thus the ultimate planetary carrying capacity for civilization. Intensive use of Earth materials has enhanced the quality of life, especially in the developed nations. Still, natural background levels, and Earth processes such as volcanic eruptions, as well as human activities involving agriculture, construction, and the extraction, refining, and transformation of mineral resources have led to harmful side effects involving environmental degradation and public health hazards. Among naturally and anthropogenically induced risks are bioaccessible airborne dusts and gases, soluble pollutants in agricultural, industrial, and residential waters, and toxic chemical species in foods and manufactured products. At appropriate levels of ingestion, many Earth materials are necessary for existence, but underdoses and overdoses have mild to serious consequences for human health and longevity. This overview briefly sketches several natural resource health hazards. Included are volcanic ash + aerosols + gases, mineral dusts, non-volcanic aerosols + nanoparticles, asbestos + fibrous zeolites, arsenic, fluorine, iodine, uranium + thorium + radium + radon + polonium, selenium, mercury, copper, lead, chromium, and cadmium. Also noted are health effects of natural disasters, and an obligatory future sustainable consumption of natural resources. Not treated are the overwhelming adverse effects of malnutrition, lack of potable water, inadequate sanitation, fossil fuel usage, mining, manufacturing, and agricultural pollution, or environmental pathogens, nor are the important impacts of complex mixtures of Earth materials considered. With rise of the worldwide information network, economic globalization, and the industrial thrust of Developing Nations, the achievement of natural resource sustainability has emerged as a strategic imperative. Accompanying increased rates of Earth materials consumption and attendant environmental change, substantially improved, universal public health will require a major global effort, integrating collaborations among geoscientists, medical researchers, and epidemiologists. Governments and NGOs must provide important support of such cooperative efforts, and both health and Earth scientists must cross disciplinary and national boundaries.

Ernst, W. G.

2012-10-01

385

Effect of natural organic materials on cadmium and neptunium sorption  

SciTech Connect

In a batch sorption study of the effect of naturally occurring organic materials on the sorption of cadmium and neptunium on oxides and tuff surfaces, the model sorbents were synthetic goethite, boehmite, amorphous silicon oxides, and a crushed tuff material from Yucca Mountain, Nevada. An amino acid, 3-(3,4-dihydroxypheny)-DL-alanine (DOPA), and an aquatic-originated fulvic material, Nordic aquatic fulvic acid (NAFA), were used as model organic chemicals. Sorption isotherm results showed that DOPA sorption followed the order aluminum oxide > iron oxide > silicon oxide and that the amount of DOAP sorption for a given sorbent increased as the solution pH was raised. The sorption of cadmium and neptunium on the iron oxide was about ten times higher than that on the aluminum oxide. The sorption of cadmium and neptunium on natural tuff material was much lower than that on aluminum and iron oxides. The sorption of cadmium on iron and aluminum oxides was found to be influenced by the presence of DOPA, and increasing the amount of DOPA coating resulted in higher cadmium sorption on aluminum oxide. However, for iron oxide, cadmium sorption decreased with increasing DOPA concentration. The presence of the model organic materials DOPA and NAFA did not affect the sorption of neptunium on tuff material or on the iron and aluminum oxides. Spectroscopic results indicate that cadmium complexes strongly with DOPA. Therefore, the effect of the organic material, DOPA, on the cadmium sorption is readily observed. However, neptunium is possibly complexed weakly with organic material. Thus, DOPA and NAFA have little effect on neptunium sorption on all sorbents selected for study.

Kung, K.S.; Triay, I.R.

1994-10-01

386

Smart composite materials for non-invasive structural health monitoring and composites manufacturing process monitoring  

NASA Astrophysics Data System (ADS)

Self-sensing composite materials with nanoscale sensor networks can provide feedback about quality evolution during composites manufacturing as well as long-term structural health. Multi-scale composites spanning nano to macro scales involve the interaction between components of varying length scales. An example of such an interaction is the influence of hollow glass microspheres on the electrical conductivity and strain sensitivity of novel carbon nanotube-based syntactic foams. In addition to uniformly dispersed carbon nanotube networks, selective integration of carbon nanotubes has been studied in form of carbon nanotube sheets and carbon nanotube sizing agents. Both techniques enable one-step carbon nanotube integration. Carbon nanotube sheets have been found to be especially useful for prepreg composites. In addition to piezoresistive-based sensing, time domain reflectometry has been studied and the strain response of time domain reflectometry sensors has been modeled and validated. Carbon nanotubes have been found to increase the strain response and damage sensitivity of time domain reflectometry sensors due to breakage of carbon nanotube networks. Two-dimensional deformation mapping and damage sensing has been implemented on composite panels using both piezoresistivity and time domain reflectometry. For the first time, high accuracy cure monitoring has been achieved using non-invasive time domain reflectometry sensors.

Pandey, Gaurav

387

Radioactivity of natural and artificial building materials - a comparative study.  

PubMed

Building materials and their additives contain radioactive isotopes, which can increase both external and internal radioactive exposures of humans. In this study Hungarian natural (adobe) and artificial (brick, concrete, coal slag, coal slag concrete and gas silicate) building materials were examined. We qualified 40 samples based on their radium equivalent, activity concentration, external hazard and internal hazard indices and the determined threshold values of these parameters. Absorbed dose rate and annual effective dose for inhabitants living in buildings made of these building materials were also evaluated. The calculations are based on (226)Ra, (232)Th and (40)K activity concentrations determined by gamma-ray spectrometry. Measured radionuclide concentrations and hence, calculated indices and doses of artificial building materials show a rather disparate distribution compared to adobes. The studied coal slag samples among the artificial building materials have elevated (226)Ra content. Natural, i.e. adobe and also brick samples contain higher amount of (40)K compared to other artificial building materials. Correlation coefficients among radionuclide concentrations are consistent with the values in the literature and connected to the natural geochemical behavior of U, Th and K elements. Seven samples (coal slag and coal slag concrete) exceed any of the threshold values of the calculated hazard indices, however only three of them are considered to be risky to use according to the fact that the building material was used in bulk amount or in restricted usage. It is shown, that using different indices can lead to different conclusions; hence we recommend considering more of the indices at the same time when building materials are studied. Additionally, adding two times their statistical uncertainties to their values before comparing to thresholds should be considered for providing a more conservative qualification. We have defined radon hazard portion to point to the limitations of the internal hazard considerations based on only measured (226)Ra activity concentrations without direct radon measurements. Our data are compared to those obtained in other countries and they provide a good basis to expand the database of radioactivity of building materials and gives information about the safety and situation of the building material industry in this central region of Europe. PMID:23246704

Szabó, Zs; Völgyesi, P; Nagy, H É; Szabó, Cs; Kis, Z; Csorba, O

2013-04-01

388

Impact damage analysis of balsawood sandwich composite materials  

NASA Astrophysics Data System (ADS)

In this study, a new composite sandwich structure with a balsa wood core (end grain and regular balsa) in conjunction with E-glass/epoxy face sheets was proposed, fabricated, impact tested, and modeled. The behavior of the sandwich structure under low velocity impact and compression after impact was investigated. Low velocity impact tests were carried out by drop-weight impact tower at different energy levels (8J-35J) to evaluate the impact response of the sandwich structure. Visual inspection, destructive and non destructive evaluation methods have been conducted. For the sandwich plate with end grain core, the damage was very clear and can be visually detected. However, the damage in regular balsa core was not clearly visible and destructive evaluation method was used. Compression testing was done after subjecting the specimens to impact testing. Impact test results; load-time, load-deflection history and energy absorption for sandwich composites with two different cores, end grain and regular balsa were compared and they were investigated at three different impact energies. The results show that the sandwich structures with end grain core are able to withstand impact loading better than the regular balsa core because the higher stiffness of end grain core informs of sustaining higher load and higher overall energy. The results obtained from compression after impact testing show that the strengths of sandwich composites with end grain and regular balsa cores were reduced about 40% and 52%, respectively, after impact. These results were presented in terms of stress-strain curves for both damaged and undamaged specimens. Finite element analysis was conducted on the sandwich composite structure using LS-DYNA code to simulate impact test. A 3- D finite element model was developed and appropriate material properties were given to each component. The computational model was developed to predict the response of sandwich composite under dynamic loading. The experimental and finite element results were matched better for maximum load. However progressive damage accumulation could not predicted well due to lack of sophisticated material damage models in FEA codes.

Abdalslam, Suof Omran

389

Thermophysical characterization of composite materials under transient heating conditions  

NASA Technical Reports Server (NTRS)

Thermophysical property measurements were made under transient heating conditions on several materials being considered for use in SCOUT rocket motors. The materials included were ATJ graphite, MX 2600 silica phenolic, FM 5272 cellulose phenolic, and two carbon-carbon composites: CARBITEX 700 and RPP-4. The ATJ was included as a reference or base line material to check performance of the transient tests as it was not expected to be sensitive to heating rate. Measurements included in the program were thermal conductivity, strength, compressive stress-strain (carbon-carbon only), thermal expansion and the effective thermal expansion under partially restrained conditions. Development of this latter measurement was a major part of the program. It consisted of partially restraining the expansion of a specimen as it was heated, measuring the load and strain which occurred (together with a simultaneous modulus determination by superimposing a small cyclic load) and using these quantities to calculate what the effective thermal expansion would have to be to produce the observed stress and deformation. For materials which are sensitive to heating rate, such as reinforced phenolics, it was believed that this would provide a more realistic determination of the thermal expansion as it more nearly simulates the conditions experienced in end use.

Roetling, J.; Hanson, J.

1972-01-01

390

Dynamic fracture of functionally graded magnetoelectroelastic composite materials  

NASA Astrophysics Data System (ADS)

The stress, magnetic and electric field analysis of multifunctional composites, weakened by impermeable cracks, is of fundamental importance for their structural integrity and reliable service performance. The aim is to study dynamic behavior of a plane of functionally graded magnetoelectroelastic composite with more than one crack. The coupled material properties vary exponentially in an arbitrary direction. The plane is subjected to anti-plane mechanical and in-plane electric and magnetic load. The boundary value problem described by the partial differential equations with variable coefficients is reduced to a non-hypersingular traction boundary integral equation based on the appropriate functional transform and frequency-dependent fundamental solution derived in a closed form by Radon transform. Software code based on the boundary integral equation method (BIEM) is developed, validated and inserted in numerical simulations. The obtained results show the sensitivity of the dynamic stress, magnetic and electric field concentration in the cracked plane to the type and characteristics of the dynamic load, to the location and cracks disposition, to the wave-crack-crack interactions and to the magnitude and direction of the material gradient.

Stoynov, Y.; Dineva, P.

2014-11-01

391

Fabricating Composite-Material Structures Containing SMA Ribbons  

NASA Technical Reports Server (NTRS)

An improved method of designing and fabricating laminated composite-material (matrix/fiber) structures containing embedded shape-memory-alloy (SMA) actuators has been devised. Structures made by this method have repeatable, predictable properties, and fabrication processes can readily be automated. Such structures, denoted as shape-memory-alloy hybrid composite (SMAHC) structures, have been investigated for their potential to satisfy requirements to control the shapes or thermoelastic responses of themselves or of other structures into which they might be incorporated, or to control noise and vibrations. Much of the prior work on SMAHC structures has involved the use SMA wires embedded within matrices or within sleeves through parent structures. The disadvantages of using SMA wires as the embedded actuators include (1) complexity of fabrication procedures because of the relatively large numbers of actuators usually needed; (2) sensitivity to actuator/ matrix interface flaws because voids can be of significant size, relative to wires; (3) relatively high rates of breakage of actuators during curing of matrix materials because of sensitivity to stress concentrations at mechanical restraints; and (4) difficulty of achieving desirable overall volume fractions of SMA wires when trying to optimize the integration of the wires by placing them in selected layers only.

Turner, Travis L.; Cano, Roberto J.; Lach, Cynthia L.

2003-01-01

392

Effect of fiber and matrix maximum strain on the energy absorption of composite materials  

NASA Technical Reports Server (NTRS)

Static crushing tests were conducted on graphite composite tubes to examine the influence of fiber and matrix maximum strain at failure on the energy absorption capability of graphite reinforced composite material. Fiber and matrix maximum strain at failure were determined to significantly effect energy absorption. The higher strain at failure composite material system, AS-4/5245, exhibited superior energy absorption capability compared to AS-4/934, T300/5245 or T300/934 composite material. Results of this investigation suggest that to achieve maximum energy absorption from a composite material a matrix material that has a higher strain at failure than the fiber reinforcement should be used.

Farley, G. L.

1985-01-01

393

Nanocelluloses: a new family of nature-based materials.  

PubMed

Cellulose fibrils with widths in the nanometer range are nature-based materials with unique and potentially useful features. Most importantly, these novel nanocelluloses open up the strongly expanding fields of sustainable materials and nanocomposites, as well as medical and life-science devices, to the natural polymer cellulose. The nanodimensions of the structural elements result in a high surface area and hence the powerful interaction of these celluloses with surrounding species, such as water, organic and polymeric compounds, nanoparticles, and living cells. This Review assembles the current knowledge on the isolation of microfibrillated cellulose from wood and its application in nanocomposites; the preparation of nanocrystalline cellulose and its use as a reinforcing agent; and the biofabrication of bacterial nanocellulose, as well as its evaluation as a biomaterial for medical implants. PMID:21598362

Klemm, Dieter; Kramer, Friederike; Moritz, Sebastian; Lindström, Tom; Ankerfors, Mikael; Gray, Derek; Dorris, Annie

2011-06-01

394

Quantum Mechanics reconstruction from invariance of the laws of nature under tensor composition  

E-print Network

Quantum and classical mechanics are derived using four natural physical principles: (1) the laws of nature are invariant under time evolution, (2) the laws of nature are invariant under tensor composition, (3) the laws of nature are relational, and (4) positivity (the ability to define a physical state). Quantum mechanics is singled out by a fifth experimentally justified postulate: nature violates Bell's inequalities.

Florin Moldoveanu

2014-07-29

395

Green engineering: Green composite material, biodiesel from waste coffee grounds, and polyurethane bio-foam  

NASA Astrophysics Data System (ADS)

In this thesis we developed several ways of producing green materials and energy resources. First, we developed a method to fabricate natural fibers composites, with the purpose to develop green textile/woven composites that could potentially serve as an alternative to materials derived from non-renewable sources. Flax and hemp fabrics were chosen because of their lightweight and exceptional mechanical properties. To make these textile/woven composites withstand moist environments, a commercially available marine resin was utilized as a matrix. The tensile, three-point bending, and edgewise compression strengths of these green textile/woven composites were measured using ASTM protocols. Secondly, we developed a chemical procedure to obtain oil from waste coffee grounds; we did leaching and liquid extractions to get liquid oil from the solid coffee. This coffee oil was used to produce bio-diesel that could be used as a substitute for petroleum-based diesel. Finally, polyurethane Bio-foam formation utilized glycerol that is the by-product from the biodiesel synthesis. A chemical synthesis procedure from the literature was used as the reference system: a triol and isocynate are mixed to produce polyurethane foam. Moreover, we use a similar triol, a by-product from bio-diesel synthesis, to reproduce polyurethane foam.

Cheng, Hsiang-Fu

396

A normalization method for life-time prediction of composite materials  

E-print Network

Introduction Industrials are increasingly using more composite materi- als in various fields particularly in aviation and automobiles fields. Their great advantage is their strength and stiffness associated are given. 2 Materials and test 2.1 Materials The studied materials were manufactured by moulding composite

Paris-Sud XI, Université de

397

Hunting composite vector resonances at the LHC: naturalness facing data  

NASA Astrophysics Data System (ADS)

We introduce a simplified low-energy effective Lagrangian description of the phenomenology of heavy vector resonances in the minimal composite Higgs model, based on the coset SO(5)/SO(4), analysing in detail their interaction with lighter top partners. Our construction is based on robust assumptions on the symmetry structure of the theory and on plausible natural assumptions on its dynamics. We apply our simplified approach to triplets in the representations ( 3, 1) and ( 1, 3) and to singlets in the representation ( 1, 1) of SO(4). Our model captures the basic features of their phenomenology in terms of a minimal set of free parameters and can be efficiently used as a benchmark in the search for heavy spin-1 states at the LHC and at future colliders. We devise an efficient semi-analytic method to convert experimental limits on ? × BR into bounds on the free parameters of the theory and we recast the presently available 8 TeV LHC data on experimental searches of spin-1 resonances as exclusion regions in the parameter space of the models. These latter are conveniently interpreted as a test of the notion of naturalness.

Greco, Davide; Liu, Da

2014-12-01

398

New composites based on poly(3-trimethylsilyltricyclononene-7) and organic nature fillers (calixarenes & cyclodextrins)  

NASA Astrophysics Data System (ADS)

Herein we describe new materials for membrane gas separation process with improved selectivities towards different pairs of gases. Organic nature fillers (modified calix[4]arenes, calix[8]arenes and modified ?-, ?-, ?-cyclodextrins) were used as additives to poly(trimethylsilyltricyclononene-7) (PTCNSi1)in order to study correlations between structure of the filling agent and gas transport parameters of the composite membranes. It was shown a positive influence of calixarenes and cyclodextrins as additives on permselectivity of the membranes. For instance, selectivity towards H2/CH4 gas pair increased almost in 2.4 times when calix[4]arene with Et- and tert-Bu- group was introduced into polymeric matrix. Detailed study of the PTCNSi1 adsorbtion/desortion data is presented. The obtained composites were characterized by TEM, WAXD, PALS and BET analysis.

Chapala, Pavel P.; Bermeshev, Maxim V.; Starannikova, Ludmila E.; Gavrilova, Natalie N.; Shantarovich, Victor P.; Filatova, Marina P.; Krut'ko, Ekaterina B.; Yampolskii, Yurii P.; Finkelshtein, Eugene Sh.

2014-05-01

399

Composition, lattice parameters, and room temperature elastic constants of natural single crystal xenotime from Novo Horizonte  

NASA Astrophysics Data System (ADS)

The composition, lattice parameters, and elastic constants of natural single crystal YPO4 xenotime from Novo Horizonte (Brazil) were determined using EPMA, XRD, and the pulse-echo technique. The composition indicates a 24% substitution of Y sites with other rare-earth elements. The lattice parameters of the studied crystal deviated only slightly from those reported for synthetic YPO4 and were in a good agreement with trends obeyed by other orthophosphates with the xenotime structure. The measured elastic constants C 11, C 33, C 44, and C 66 were consistent with synthetic crystals when porosity was accounted for. C 12 and C 13 constants were evaluated based on the comparison with other materials with xenotime structure. The elastic constants could be rationalized using interionic force constants and bond energies.

Mogilevsky, P.; Zaretsky, E. B.; Parthasarathy, T. A.; Meisenkothen, F.

2006-12-01

400

Modelling the shock response of a damageable anisotropic composite material  

NASA Astrophysics Data System (ADS)

The purpose of this paper is the investigation of the effect of fibre orientation on the shock response of a damageable carbon fibre-epoxy composite (CFEC). A carbon fibre-epoxy composite (CFEC) shock response in the through-thickness orientation and in one of the fibre directions is significantly different. Modelling the effect of fibre orientation on the shock response of a CFEC has been performed using a generalised decomposition of the stress tensor [A.A. Lukyanov, Int. J. Plasticity 24, 140 (2008)] and an accurate extrapolation of high-pressure shock Hugoniot states to other thermodynamics states for shocked CFEC materials. The analysis of the experimental data subject to the linear relation between shock velocities and particle velocities has shown that damage softening process produces discontinuities both in value and slope in the generalized bulk shock velocity and particle velocity relation [A.A. Lukyanov, Eur Phys J B 74, 35 (2010)]. Therefore, in order to remove these discontinuities, the three-wave structure (non-linear anisotropic, fracture and isotropic elastic waves) that accompanies damage softening process is proposed in this work for describing CFEC behavior under shock loading. A numerical calculation shows that Hugoniot Stress Levels (HELs) agree with the experimental data for selected CFEC material in different directions at low and at high intensities. In the through-thickness orientation, the material behaves similar to a simple polymer. In the fibre direction, the proposed model explains a pronounced ramp, before at sufficiently high stresses, and a much faster rising shock above it. The results are presented and discussed, and future studies are outlined.

Lukyanov, Alexander A.

2012-09-01

401

2014 Global Conference on Polymer and Composite Materials (PCM 2014)  

NASA Astrophysics Data System (ADS)

The 2014 Global Conference on Polymer and Composite Materials (PCM 2014) sponsored by Ningbo Adhesives and Products Industry Association, Shanghai Bonding Technology Association, Zhejiang Bonding Technology Association, Wuhan Bonding Technology Association, Hebei Bonding and Coatings Association and Polyurethane Industry Association was held from May 27 to May 29 2014 in Ningbo, China. The technical program consisted of 8 international keynote speakers, oral presentations, and a poster session. The conference also included an industrial exhibition where more than 50 companies displayed in their booths their most recent advanced products and services. The present issue of IOP Conference Series: Materials Science and Engineering (MSE) records the proceedings of PCM 2014 and contains 37 specially selected manuscripts submitted to PCM2014 conference. The electronic submission and handling of manuscripts via the conference website, including the selection of reviewers and evaluation of manuscripts, were identical to the procedures applied to manuscripts submitted as regular contributions for publication. The organization of this conference and the preparation of proceedings volumes would have been impossible without the tremendous efforts and dedication of many individuals, especially from Ms. Yin Pan, who oversaw the organization of the conference and the program; and a large team of reviewers with their timely submission of quality reports. We express our sincere thanks to all authors and presenters for their contributions. We also thank very much our sponsors for their generous support. The 2015 Global Conference on Polymer and Composite Materials (PCM2015) will be held in Beijing, China on May 16-18, 2015. Beijing, the capital of the People's Republic of China and one of the most populous cities in the world, will welcome to all participants for a renewed and vibrant conference. Prof. Dr. Esteban Broitman Linköping University, Sweden Editor in Chief — PCM2014

2014-08-01

402

Low-Cost Composite Materials for Polymer Electrolyte Fuel Cell Bipolar Plates  

SciTech Connect

Polymer electrolyte fuel cells (PEFCS) are under widespread development to produce electrical power for a variety of stationary and transportation applications. To date, the bipolar plate remains the most problematic and costly component of PEFC stacks (1). In addition to meeting cost constraints, bipolar plates must possess a host of other properties, the most important of which are listed in Table 1. The most commonly used material for single cell testing is machined graphite, which is expensive and costly to machine. The brittle nature of graphite also precludes the use of thin components for reducing stack size and weight, which is particularly important for transportation applications. Other stack designs consider the use of metal hardware such as stainless steel (2,3). But a number of disadvantages are associated with stainless steel, including high density, high cost of machining, and possible corrosion in the fuel cell environment. In light of these difficulties, much of the recent work on fuel cell bipolar plate materials has concentrated on graphite/polymer composites (4--8). Composite materials offer the potential advantages of lower cost, lower weight, and greater ease of manufacture than traditional graphite and metal plates. For instance, flow fields can be molded directly into these composites, thereby eliminating the costly and difficult machining step required for graphite or metal hardware.

Busick, D.N.; Wilson, M.S.

1998-11-01

403

Three-dimensional nuclear magnetic resonance and x-ray microtomographic imaging of composite materials  

SciTech Connect

This paper presents a new-three-dimensional nuclear magnetic resonance (NMR) imaging technique for nondestructive evaluation of green-state ceramic composite materials. The technique is based on a 3-D backprojection protocol for data acquisition combined with a Radon reconstruction technique. Particularly for NMR of solid materials, this imaging protocol can provide higher three dimensional spatial resolution than is possible with commonly applied slice-selection protocols. The applicability of this 3-D NMR imaging technique was demonstrated using whisker-reinforced Si{sub 3}N{sub 4}/Si{sub 3}N{sub 4} ceramic composites. While NMR is a sensitive and unique method for spatial discrimination of chemical properties (e.g., organic distributions), x-ray CT is a sensitive and proven technique for determining variations in density (i.e., voids and inclusions) within an object. The complementary nature of these two techniques was shown by imaging a piece of green ceramic composite material by both NMR and x-ray microtomography techniques.

Dieckman, S.L.; Gopalsami, N.; Botto, R.E. (Argonne National Lab., IL (USA)); Rizo, P. (CEA Centre d'Etudes Nucleaires de Grenoble, 38 (France). Lab. d'Electronique et de Technologie de l'Informatique)

1990-01-01

404

An applied investigation of kenaf-based fiber/polymer composites as potential lightweight materials for automotive components  

NASA Astrophysics Data System (ADS)

Natural fibers have the potential to replace glass fibers in fiber-reinforced composite applications. However, the natural fibers' intrinsic properties cause these issues: (1) the mechanical property variation; (2) moisture uptake by natural fibers and their composites; (3) lack of sound, cost-effective, environment-friendly fiber-matrix compounding processes; (4) incompatibility between natural fibers and polymer matrices; and (5) low heat-resistance of natural fibers and their composites. This dissertation systematically studied the use of kenaf bast fiber bundles, obtained via a mechanical retting method, as a light-weight reinforcement material for fiber-reinforced thermoset polymer composites for automotive applications. Kenaf bast fiber bundle tensile properties were tested, and the effects of locations in the kenaf plant, loading rates, retting methods, and high temperature treatments and their durations on kenaf bast fiber bundle tensile properties were evaluated. A process has been developed for fabricating high fiber loading kenaf bast fiber bundle-reinforced unsaturated polyester composites. The generated composites possessed high elastic moduli and their tensile strengths were close to specification requirements for glass fiber-reinforced sheet molding compounds. Effects of fiber loadings and lengths on resultant composite's tensile properties were evaluated. Fiber loadings were very important for composite tensile modulus. Both fiber loadings and fiber lengths were important for composite tensile strengths. The distributions of composite tensile, flexural and impact strengths were analyzed. The 2-parameter Weibull model was found to be the most appropriate for describing the composite strength distributions and provided the most conservative design values. Kenaf-reinforced unsaturated polyester composites were also proved to be more cost-effective than glass fiber-reinforced SMCs at high fiber loadings. Kenaf bast fiber bundle-reinforced composite's water absorption properties were tested. Surface-coating and edge-sealing significantly reduced composite water resistance properties. Encapsulation was a practical method to improve composite water resistance properties. The molding pressure and styrene concentrations on composite and matrix properties were evaluated. Laser and plasma treatment improved fiber-to-matrix adhesion.

Du, Yicheng

405

Water-responsive rapid recovery of natural cellular material.  

PubMed

Insight into the stimuli-responsive behaviour of biological materials with hierarchical microstructures is essential for designing new sustainable materials and structures. Shape memory, self-healing and self-repairing will become valuable characteristics of advanced materials. Here we report the water-triggered shape recovery of a natural biological material, the luffa sponge. The longitudinally crushed luffa sponge column can recover up to 98% of its original shape after it is immersed in water. The mechanical properties of the luffa sponge can also be recovered, to a large extent, after a subsequent drying process. The effects of strain rate, crushing strains, loading cycles, and temperature/duration of water treatment of the drying process on the shape recovery ratio and the energy dissipation recovery ratio have been investigated. The results from this study have demonstrated that the luffa sponge material possesses remarkable shape memory effects and mechanical recovery features which could be exploited or biomimicked for the design of water-responsive smart materials undergoing large deformations. PMID:24657743

Shen, Jianhu; Xie, Yi Min; Zhou, Shiwei; Huang, Xiaodong; Ruan, Dong

2014-06-01

406

Thermal Energy in Carbon Nanotube and Graphene Composite Materials  

NASA Astrophysics Data System (ADS)

Low-dimensional materials, like carbon nanotubes (CNTs) and graphene, possess extraordinary properties---higher thermal conductivity than any bulk material, mechanical strength 10-100 times greater than steel on a mass basis, and electrical current capacity 1000 times greater than copper. While composites incorporating these low-dimensional materials promise solutions to global sustainability challenges, significant transport barriers exist at the matrix interface that influence the composite properties. My PhD research sought to address this knowledge gap. I've experimentally explored how CNTs and graphene impact thermal conductivity when added in small volume fractions to gases, liquids and solids through the study of CNT aerogels (ultra lightweight, 8 kg/m3, 99.6% void space), and phase change nanocomposites (hexadecane-graphene). I measured the thermal conductivity of the CNT aerogel with various filling gases versus pressure using a novel technique that targeted ultralow thermal conductivity materials, called metal-coated 3o. I observed amplified energy transport length scales resulting from low gas accommodation, which is a general feature of carbon based nanoporous materials. Our evidence also shows that despite the high thermal conductivity of CNTs, thermal conduction through the CNT network is limited by the high thermal boundary resistance at van der Waals bonded CNT junctions. In the second system, I studied thermal and electrical conductivity of hexadecane- multi-layered-graphene (MLG) phase change nanocomposites to understand how morphology of the MLG network impacts transport. By adjusting the freezing rate, the electrical conductivity in the solid phase can be tuned between 1 and 5 orders-of-magnitude and the solid-liquid thermal conductivity ratio can be varied between 2.6 to 3.0. This research has yielded interesting insights into the tunability of nanocomposites and the physics underlying it, including evidence to indicate that the presence of graphene actually enhances the thermal conductivity of the hexadecane itself. Future work here might address how the graphene influences the properties of the hexadecane.

Schiffres, Scott N.

407

Effects of the methyltrimethoxysilane coupling agent on phenolic and miscanthus composites containing calcium sulfite scrubber material  

NASA Astrophysics Data System (ADS)

The purpose of this research is to test the effects of methyltrimethoxysilane coupling agent on composite material containing calcium sulfite obtained from the Southern Illinois Power Co-operative. This scrubber material and the miscanthus plant are of interest due to their use in coal burning power plants to reduce toxic emission. When calcium sulfate is passed through coal fire gas emissions it absorbs mercury and sulfur. In these composites it is used as filler to reduce cost. Miscanthus is a source of both cellulose reinforcement and some natural resin. This plant has low care requirements, little mineral content, useful energy return, and positive environmental effects. Under investigation is whether a post-cure procedure or a silane coupling agent will positively impact the composite. Hot pressing alone may not be enough to fully cure the phenolic. It is hoped that the silane will increase the strength characteristics of the composite by enhancing adhesion between the calcium sulfite and phenolic resin. Possible effects on the miscanthus by the silane will also be tested. Phenolic is being utilized because of its recycling and biodegradable properties along with cost effectiveness in mass production. Composite mechanical performance was measured through 3-point bending to measure flexural strength and strain at breakage. A dynamic mechanical analyzer (DMA) was used to find thermomechanical properties. The post-cure was found to be effective, particularly on the final composite containing silane. When methyltrimethoxysilane was added to the miscanthus prior to fabrication, it was found to reduce flexural strength and density. However the addition of methyltrimethoxysilane to the calcium sulfite altered thermo-mechanical properties to a state more like pure phenolic, with added flexibility and thermal stability.

Jones, Sean

408

Organic materials in planetary and protoplanetary systems: nature or nurture?  

NASA Astrophysics Data System (ADS)

Aims: The objective of this work is to summarize the discussion of a workshop aimed at investigating the properties, origins, and evolution of the materials that are responsible for the red coloration of the small objects in the outer parts of the solar system. Because of limitations or inconsistencies in the observations and, until recently, the limited availability of laboratory data, there are still many questions on the subject. Our goal is to approach two of the main questions in a systematic way: - Is coloring an original signature of materials that are presolar in origin ("nature") or stems from post-formational chemical alteration, or weathering ("nurture")? - What is the chemical signature of the material that causes spectra to be sloped towards the red in the visible? We examine evidence available both from the laboratory and from observations sampling different parts of the solar system and circumstellar regions (disks). Methods: We present a compilation of brief summaries gathered during the workshop and describe the evidence towards a primordial vs. evolutionary origin for the material that reddens the small objects in the outer parts of our, as well as in other, planetary systems. We proceed by first summarizing laboratory results followed by observational data collected at various distances from the Sun. Results: While laboratory experiments show clear evidence of irradiation effects, particularly from ion bombardment, the first obstacle often resides in the ability to unequivocally identify the organic material in the observations. The lack of extended spectral data of good quality and resolution is at the base of this problem. Furthermore, that both mechanisms, weathering and presolar, act on the icy materials in a spectroscopically indistinguishable way makes our goal of defining the impact of each mechanism challenging. Conclusions: Through a review of some of the workshop presentations and discussions, encompassing laboratory experiments as well as observational data, we infer that both "nature" and "nurture" are instrumental in the coloration of small objects in the outer parts

Dalle Ore, C. M.; Fulchignoni, M.; Cruikshank, D. P.; Barucci, M. A.; Brunetto, R.; Campins, H.; de Bergh, C.; Debes, J. H.; Dotto, E.; Emery, J. P.; Grundy, W. M.; Jones, A. P.; Mennella, V.; Orthous-Daunay, F. R.; Owen, T.; Pascucci, I.; Pendleton, Y. J.; Pinilla-Alonso, N.; Quirico, E.; Strazzulla, G.

2011-09-01

409

Composition and method for removing photoresist materials from electronic components  

DOEpatents

The invention is a combination of at least one dense phase fluid and at least one dense phase fluid modifier which can be used to contact substrates for electronic parts such as semiconductor wafers or chips to remove photoresist materials which are applied to the substrates during manufacture of the electronic parts. The dense phase fluid modifier is one selected from the group of cyclic, aliphatic or alicyclic compounds having the functional group: ##STR1## wherein Y is a carbon, oxygen, nitrogen, phosphorus or sulfur atom or a hydrocarbon group having from 1 to 10 carbon atoms, a halogen or halogenated hydrocarbon group having from 1 to 10 carbon atoms, silicon or a fluorinated silicon group; and wherein R.sub.1 and R.sub.2 can be the same or different substituents; and wherein, as in the case where X is nitrogen, R.sub.1 or R.sub.2 may not be present. The invention compositions generally are applied to the substrates in a pulsed fashion in order to remove the hard baked photoresist material remaining on the surface of the substrate after removal of soft baked photoresist material and etching of the barrier layer.

Davenhall, Leisa B. (Santa Fe, NM); Rubin, James B. (Los Alamos, NM)

2002-01-01

410

Reinforcements: The key to high performance composite materials  

NASA Technical Reports Server (NTRS)

Better high temperature fibers are the key to high performance, light weight composite materials. However, current U.S. and Japanese fibers still have inadequate high temperature strength, creep resistance, oxidation resistance, modulus, stability, and thermal expansion match with some of the high temperature matrices being considered for future aerospace applications. In response to this clear deficiency, both countries have research and development activities underway. Once successful fibers are identified, their production will need to be taken from laboratory scale to pilot plant scale. In such efforts it can be anticipated that the Japanese decisions will be based on longer term criteria than those applied in the U.S. Since the initial markets will be small, short term financial criteria may adversely minimize the number and strength of U.S. aerospace materials suppliers to well into the 21st century. This situation can only be compounded by the Japanese interests in learning to make commercial products with existing materials so that when the required advanced fibers eventually do arrive, their manufacturing skills will be developed.

Grisaffe, Salvatore J.

1990-01-01

411

The new IAEA reference material: IAEA-434 technologically enhanced naturally occurring radioactive materials (TENORM) in phosphogypsum.  

PubMed

A reliable determination of Technologically Enhanced Naturally Occurring Radioactive Materials in phosphogypsum is necessary to comply with radiation protection and environmental regulations. In this respect, a new phosphogypsum reference material was produced and certified to assist in the validation of analytical methods and the quality assurance of produced analytical results. This paper presents the sample preparation methodology, material homogeneity assessment, characterization campaign results and assignment of property values, and associated uncertainties. The reference values and associated uncertainties for Pb-210, Ra-226, Th-230, U-234 and U-238 were established based on consensus values calculated from analytical results reported by three National Metrology Institutes and five expert laboratories. PMID:20869259

Shakhashiro, A; Sansone, U; Wershofen, H; Bollhöfer, A; Kim, C K; Kim, C S; Kis-Benedek, G; Korun, M; Moune, M; Lee, S H; Tarjan, S; Al-Masri, M S

2011-01-01

412

Electrochemical performance of sulfur composite cathode materials for rechargeable lithium batteries  

Microsoft Academic Search

The structure and characteristic of carbon materials have a direct influence on the electrochemical performance of sulfur–carbon composite electrode materials for lithium–sulfur battery. In this paper, sulfur composite has been synthesized by heating a mixture of elemental sulfur and activated carbon, which is characterized as high specific surface area and microporous structure. The composite, contained 70% sulfur, as cathode in

Feng Wu; Sheng Xian Wu; Ren Jie Chen; Shi Chen; Guo Qing Wang

2009-01-01

413

On the Use of Composite Charges to Determine Insensitive Explosive Material Properties at the Laboratory Scale  

E-print Network

Full Paper On the Use of Composite Charges to Determine Insensitive Explosive Material Properties explosive charges are presented. The composite charges con- sist of a spherical booster charge surrounded by a concentric, spherical "candidate material" shell charge. By way of composite charge explosive

Settles, Gary S.

414

Preparation, characterization and application of the magadiite based mesoporous composite material of catalytic interest  

Microsoft Academic Search

The synthesis of a new type of mesoporous materials by intercalation of silica between magadiite layers was carried out. For the preparation of the composite material, reactive silica gels with compositions characteristic for the synthesis of MCM-41 were used. Samples synthesized with various compositions were characterized by X-ray diffraction, IR and NMR spectroscopy, thermal analysis, BET measurements as well as

Á. Fudala; Z. Kónya; Y. Kiyozumi; S.-I. Niwa; M. Toba; F. Mizukami; P. B. Lentz; J. Nagy; I. Kiricsi

2000-01-01

415

NUMERICAL EVALUATION OF SINGLE FIBER MOTION FOR SHORT-FIBER-REINFORCED COMPOSITE MATERIALS PROCESSING  

E-print Network

1 NUMERICAL EVALUATION OF SINGLE FIBER MOTION FOR SHORT-FIBER-REINFORCED COMPOSITE MATERIALS fibers are derived in this paper. Keywords: Jeffery's orbit, short-fiber-reinforced composite material Mechanical properties of short-fiber-reinforced composite systems are largely dependent on the fiber

Montgomery-Smith, Stephen

416

Numerical Simulation of Delamination Growth in Composite Materials  

NASA Technical Reports Server (NTRS)

The use of decohesion elements for the simulation of delamination in composite materials is reviewed. The test methods available to measure the interfacial fracture toughness used in the formulation of decohesion elements are described initially. After a brief presentation of the virtual crack closure technique, the technique most widely used to simulate delamination growth, the formulation of interfacial decohesion elements is described. Problems related with decohesion element constitutive equations, mixed-mode crack growth, element numerical integration and solution procedures are discussed. Based on these investigations, it is concluded that the use of interfacial decohesion elements is a promising technique that avoids the need for a pre-existing crack and pre-defined crack paths, and that these elements can be used to simulate both delamination onset and growth.

Camanho, P. P.; Davila, C. G.; Ambur, D. R.

2001-01-01

417

Aluminum Foam-Phase Change Material Composites as Heat Exchangers  

SciTech Connect

The effects of geometric parameters of open-cell aluminum foams on the performance of aluminum foam-phase change material (PCM) composites as heat sinks are investigated by experiments. Three types of open-cell aluminum 6061 foams with similar relative densities and different cell sizes are used. Paraffin is selected as the PCM due to its excellent thermal stability and ease of handling. The experimental results show that the performance of the heat sink is significantly affected by the surface area density of the aluminum foam. In general, as the surface area density of the foam increases, the performance of the heat sink is improved regardless of the current phase of the PCM.

Hong, Sung-tae; Herling, Darrell R.

2007-04-07

418

Study of the influence of hole quality on composite materials  

NASA Technical Reports Server (NTRS)

The influence of hole quality on the structural behavior of composite materials was investigated. From an industry survey it was determined that the most frequent imperfections encountered during hole fabrication are chipout, delamination, and oversize conditions. These hole flaw types were generated in critical areas of static, compression, and fatigue specimens fabricated from T300/5208 graphite/epoxy system. The specimens were tested in static and cyclic pin bearing modes in addition to compression loading. Results of these tests are presented and discussed. The hole chipout defect reduced the static and cyclic endurance characteristics. Oversize holes also lowered the cyclic pin bearing endurance, but had no influence of the static pin bearing characteristics. Delamination had no insignificant influence on the static tension and cyclic pin bearing characteristics. Compression tests demonstrated a deleterious effect for chipout of delamination defects. Hole quality requirements proposed are discussed.

Pengra, J. J.

1980-01-01

419

Nanoengineered thermal materials based on carbon nanotube array composites  

NASA Technical Reports Server (NTRS)

A method for providing for thermal conduction using an array of carbon nanotubes (CNTs). An array of vertically oriented CNTs is grown on a substrate having high thermal conductivity, and interstitial regions between adjacent CNTs in the array are partly or wholly filled with a filler material having a high thermal conductivity so that at least one end of each CNT is exposed. The exposed end of each CNT is pressed against a surface of an object from which heat is to be removed. The CNT-filler composite adjacent to the substrate provides improved mechanical strength to anchor CNTs in place and also serves as a heat spreader to improve diffusion of heat flux from the smaller volume (CNTs) to a larger heat sink.

Li, Jun (Inventor); Meyyappan, Meyya (Inventor)

2007-01-01

420

Nanoengineered thermal materials based on carbon nanotube array composites  

NASA Technical Reports Server (NTRS)

A method for providing for thermal conduction using an array of carbon nanotubes (CNTs). An array of vertically oriented CNTs is grown on a substrate having high thermal conductivity, and interstitial regions between adjacent CNTs in the array are partly or wholly filled with a filler material having a high thermal conductivity so that at least one end of each CNT is exposed. The exposed end of each CNT is pressed against a surface of an object from which heat is to be removed. The CNT-filler composite adjacent to the substrate provides improved mechanical strength to anchor CNTs in place and also serves as a heat spreader to improve diffusion of heat flux from the smaller volume (CNTs) to a larger heat sink.

Li, Jun (Inventor); Meyyappan, Meyya (Inventor); Dangelo, Carlos (Inventor)

2010-01-01

421

Nanoengineered Thermal Materials Based on Carbon Nanotube Array Composites  

NASA Technical Reports Server (NTRS)

A method for providing for thermal conduction using an array of carbon nanotubes (CNTs). An array of vertically oriented CNTs is grown on a substrate having high thermal conductivity, and interstitial regions between adjacent CNTs in the array are partly or wholly filled with a filler material having a high thermal conductivity so that at least one end of each CNT is exposed. The exposed end of each CNT is pressed against a surface of an object from which heat is to be removed. The CNT-filler composite adjacent to the substrate provides improved mechanical strength to anchor CNTs in place and also serves as a heat spreader to improve diffusion of heat flux from the smaller volume (CNTs) to a larger heat sink.

Li, Jun (Inventor); Meyyappan, Meyya (Inventor)

2007-01-01

422

Health Monitoring of Composite Material Structures using a Vibrometry Technique  

NASA Technical Reports Server (NTRS)

Large composite material structures such as aircraft and Reusable Launch Vehicles (RLVS) operate in severe environments comprised of vehicle dynamic loads, aerodynamic loads, engine vibration, foreign object impact, lightning strikes, corrosion, and moisture absorption. These structures are susceptible to damage such as delamination, fiber breaking/pullout, matrix cracking, and hygrothermal strain. To ensure human safety and load-bearing integrity, these structures must be inspected to detect and locate often invisible damage and faults before becoming catastrophic. Moreover, nearly all future structures will need some type of in-service inspection technique to increase their useful life and reduce maintenance and overall costs. Possible techniques for monitoring the health and indicating damage on composite structures include: c-scan, thermography, acoustic emissions using piezoceramic actuators or fiber-optic wires with gratings, laser ultrasound, shearography, holography, x-ray, and others. These techniques have limitations in detecting damage that is beneath the surface of the structure, far away from a sensor location, or during operation of the vehicle. The objective of this project is to develop a more global method for damage detection that is based on structural dynamics principles, and can inspect for damage when the structure is subjected to vibratory loads to expose faults that may not be evident by static inspection. A Transmittance Function Monitoring (TFM) method is being developed in this project for ground-based inspection and operational health monitoring of large composite structures as a RLV. A comparison of the features of existing health monitoring approaches and the proposed TFM method is given.

Schulz, Mark J.

1997-01-01

423

Microstructure characterization of multi-phase composites and utilization of phase change materials and recycled rubbers in cementitious materials  

NASA Astrophysics Data System (ADS)

This research focuses on two important subjects: (1) Characterization of heterogeneous microstructure of multi-phase composites and the effect of microstructural features on effective properties of the material. (2) Utilizations of phase change materials and recycled rubber particles from waste tires to improve thermal properties of insulation materials used in building envelopes. Spatial pattern of multi-phase and multidimensional internal structures of most composite materials are highly random. Quantitative description of the spatial distribution should be developed based on proper statistical models, which characterize the morphological features. For a composite material with multi-phases, the volume fraction of the phases as well as the morphological parameters of the phases have very strong influences on the effective property of the composite. These morphological parameters depend on the microstructure of each phase. This study intends to include the effect of higher order morphological details of the microstructure in the composite models. The higher order statistics, called two-point correlation functions characterize various behaviors of the composite at any two points in a stochastic field. Specifically, correlation functions of mosaic patterns are used in the study for characterizing transport properties of composite materials. One of the most effective methods to improve energy efficiency of buildings is to enhance thermal properties of insulation materials. The idea of using phase change materials and recycled rubber particles such as scrap tires in insulation materials for building envelopes has been studied.

Meshgin, Pania

2011-12-01

424

Ceramic Matrix Composite Cooled Nozzle Material Development Program  

NASA Technical Reports Server (NTRS)

The X-33 program initiated a risk reduction technology project to develop an actively cooled cermic matrix composite (CMC) nozzle ramp for the linear aerospike engine. The objective was to reduce the weight and increase the operating temperature capabilities of the nozzle ramp. A complement to this original project was subsequently supported by NASA's Second Generation Reusable Launch Vehicle Program to develop a high risk high payoff cooled composite nozzle ramp. This project focused on less mature technologies and concepts having the potential to achieve a significant weight reduction beyond those systems which were being considered in the original X-33 project. The aerospike engine was not selected under the initial Space Launch Initiative (SLI) Program research announcement. However, in recognition of the tremendous application opportunities of such technology to other areas and systems in the rocket industry, the effort was continued and is in the process of being transferred to the 3rd Generation Reusable Launch Vehicle (RLV) Program where it will be combined with the current cooled CMC panel project. The objective of the refocused project is to advance the material, design, and analysis work on the ramp concepts to a point that would allow the selection of the most promising candidate(s) for continued development. The concept(s) carried on in the 3rd Generation RLV Program will be modified to address the goals of this program. Originally, four contracts with different design concepts were initiated. Each contractor has performed design and analysis of their concept and submitted a subscale component for testing in the Cell 22 test rig at Glenn Research Center. This paper will discuss the results to date of each design concept and the potential applications to future rocket nozzle systems. The engineering technology challenges for each concept were determined and addressed during this phase of the effort. These challenges and the success in addressing them will also be discussed. High temperature, noneroding nozzle materials have the potential to significantly improve nozzle performance. The work performed under this effort is at the forefront of CMC material development and will give the rocket nozzle community a good view into the status of cooled CMC materials.

Lawrence, Tim; Eckel, Andy; Porter, John; Pichon, T.; Patterson, B.; Paquette, T.

2002-01-01

425

The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials  

NASA Technical Reports Server (NTRS)

During the three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. At the time the grant started, our collaborating PI, Dante Lauretts, was a postdoctoral research associate working with Peter Buseck at Arizona State University. The work on chondritic Hg was done in collaboration with Dante Lauretta and Peter Buseck and this study was published in Lauretta et a1 (2001a). In July, 2001 Dante Lauretta accepted a position as an Assistant Professor in the Lunar and Planetary Laboratory at the University of Arizona. His funding was transferred and this grant has supported much of his research activities during his first two years at the U of A. Several other papers are in preparation and will be published soon. We presented papers on this topic at Goldschmidt Conferences, the Lunar and Planetary Science Conferences, and the Annual Meetings of the Meteoritical Society. The work done under this grant has spurred several new directions of inquiry, which we are still pursuing. Included in this paper are the studies of bulk abundances and isotopic compositions of metreoritic Mercury, and the development of a thermal analysis ICP-MS technique applied to thermally liable elements.

Blum, J. D.; Klaue, Bjorn

2005-01-01

426

Mechanistic Effects of Porosity on Structural Composite Materials  

NASA Astrophysics Data System (ADS)

As fiber reinforced composites continue to gain popularity as primary structures in aerospace, automotive, and powersports industries, quality control becomes an extremely important aspect of materials and mechanical engineering. The ability to recognize and control manufacturing induced defects can greatly reduce the likelihood of unexpected catastrophic failure. Porosity is the result of trapped volatiles or air bubbles during the layup process and can significantly compromise the strength of fiber reinforced composites. A comprehensive study was performed on an AS4C-UF3352 TCR carbon fiber-epoxy prepreg system to determine the effect of porosity on flexural, shear, low-velocity impact, and damage residual strength properties. Autoclave cure pressure was controlled to induce varying levels of porosity to construct six laminates with porosity concentrations between 0-40%. Porosity concentrations were measured using several destructive and nondestructive techniques including resin burnoff, sectioning and optical analysis, and X-ray computed tomography (CT) scanning. Ultrasonic transmission, thermography, and CT scanning provided nondestructive imaging to evaluate impact damage. A bilinear relationship accurately characterizes the change in mechanical properties with increasing porosity. Strength properties are relatively unaffected when porosity concentrations are below approximately 2.25% and decrease linearly by up to 40% in high porosity specimens.

Siver, Andrew

427

Permeability testing of composite material and adhesive bonds for the DC-XA composite feedline program  

NASA Technical Reports Server (NTRS)

Hercules IM7/8552 carbon/epoxy and Hysol EA 9394 epoxy adhesive bonded between composite/titanium were tested for permeability after various numbers of thermal cycles between 100 C and liquid nitrogen (-196 C). The specimens were quenched from the 100 C temperature into liquid nitrogen to induce thermal shock into the material. Results showed that the carbon/epoxy system was practically impermeable even after 12 thermal cycles. The EA 9394 adhesive bondline was more permeable than the carbon/epoxy, but vacuum mixing minimized the permeability and kept it within allowable limits. Thermal cycling had little effect on the permeability values of the bondline specimens.

Nettles, A. T.

1995-01-01

428

2006 Nature Publishing Group Graphene-based composite materials  

E-print Network

. 1a). In contrast to pristine graphite, the graphene- derived sheets in graphite oxide (graphene of these functional groups makes graphene oxide sheets strongly hydrophilic, which allows graphite oxide to readily, such as one-third, and so on), we believe that these represent fully exfoliated graphene oxide sheets. In fact

429

Inhibition of catalytic oxidation of carbon/carbon composite materials  

NASA Astrophysics Data System (ADS)

An investigation coupling experimental efforts with computational chemistry analysis was conducted to study the inhibition effects of phosphorous or boron on the oxidation of carbon/carbon composite materials catalyzed by potassium or calcium acetate (KAC or CaAC). Commercial aircraft brakes were used, which are exposed during use to K- or Ca-containing runway deicing agents. The reactivity of inhibitor-doped carbon materials was determined by temperature programmed oxidation (TPO) and isothermal oxidation in 1 atm O2. The structure and surface chemistry of inhibitor-doped samples were characterized, and the inhibition mechanisms were explored with the help of ab initio molecular orbital calculations. The catalytic effects of KAC or CaAC were found to be dependent on catalyst loading, pretreatment procedure, temperature and O2 partial pressure. Experimental observations showed that K is a more effective catalyst for carbon composite</